Cytidine nucleoside compound

ABSTRACT

5&#39;-Esters of ara-cytidine (1-β-D-arabinofuranosylcytosine) are prepared by reacting ara-cytidine with β,β,β-trihaloethoxycarbonyl halide or other protective agency to form a protective amido group on the primary amino nitrogen of ara-cytidine and then reacting the thus-protected compound with a reagent reactive with the 5&#39;-O-hydroxyl group, e.g., an acylating agent, to form the 5&#39;-O-derivative. The β,β,β-trihaloethoxycarbonyl or other protective group is then removed. Alternately, the primary amino group of ara-cytidine can be protected from acylation by protonation. The 5&#39;-O-derivatives in their free base of salt form are characterized in that they display the property of sustained release of the compound, ara-cytidine, when administered intramuscularly or subcutaneously. Ara-cytidine is known for its anti-viral action and for its usefulness as an agent for controlling leukemias, including acute leukemia, and the sustained release property extends the usefulness of ara-cytidine for these purposes and as an inmunosuppressive agent. The 5&#39;-O-derivartives of this invention can also be administered orally.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a division of application Ser. No. 593,890, filed July 7, 1975,now abandoned which is a continuation-in-part of application Ser. No.427,183, filed Dec. 21, 1973, now abandoned which application is acontinuation of application Ser. No. 11,826, filed Feb. 16, 1970, nowU.S. Pat. No. 3,847,898, which application is a continuation-in-part ofapplication Ser. No. 828,380, filed May 27, 1969, now abandoned.

In application Ser. No. 745,096, now U.S. Pat. No. 3,547,905 issued Dec.15, 1970, there is disclosed 1-β-D-arabinofuranosylcytosine5'-(1-adamantanecarboxylate), described as possessing sustained releaseproperties and a "depot" effect. The compound was synthesized by directadamantoylation of ara-cytidine to form first the bisadamantoylcompound, and then selective hydrolysis gave the 5'-O-adamantoyl ester.

BACKGROUND OF THE INVENTION

Ara-cytidine, also called cytarabine, cytosine arabinoside, or CA, hasbeen known for some time as an effective agent for controlling growth ofcertain kinds of cancers, especially leukemia. Its use has beenhampered, however, because of difficulties in establishing andmaintaining effective and sustained contact between the compound and thecells under treatment.

BRIEF DESCRIPTION OF THE INVENTION

The 5'-O-derivatives, including principally esters, of this inventionare prepared by first blocking or protecting the primary amino nitrogenor ara-cytidine with β,β,β-trihaloethoxycarbonyl group wherein "halo" ischlorine or bromine, and "halide" is chloride, bromide or iodide, andthen causing the blocked compound to react with an agency capable ofreacting with the 5'-O-hydroxyl substituent. There result the5'-O-derivatives of this invention. The method of this invention, whichprovides an effective blocking of the primary amino nitrogen, is lesswasteful of esterifying agent, and being higher overall-yielding, isalso less wasteful of the expensive substance, ara-cytidine. The methodrenders available a wide range of novel and useful 5'-O-derivatives aswill be discussed below.

The compounds of this invention include salts of the 5'-O-derivativeswith pharmaceutically acceptable mineral or organic acids having a pKabout or less than 2.

The compounds of this invention when administered exhibit the propertiescharacteristic of ara-cytidine, and in addition exhibit the desirableproperty of sustained release of ara-cytidine over periods of time afteradministration. Thus the modes of administration and dosages for use arethose conventionally used with ara-cytidine. For example, they can beadministered orally or intramuscularly. Their use intravenously isfeasible, but the need for such disadvantageous devices as theintravenous drip is obviated by the sustained release of "depot" effectof the novel compounds.

In addition, the compounds of this invention exhibit antiphageproperties, and, used in conjunction with a deaminase inhibitor, can beused to protect a fermentation threatened with contamination by a phage.

The ester compounds of this invention have the activities and uses thatcharacterize the unesterified compound, cytarabine or ara-cytidine,namely, activity against acute leukemia and against lymphosarcoma, asdisclosed in U.S. application Ser. No. 627,645, filed Apr. 3, 1967, nowU.S. Pat. No. 3,444,294. As in the case of ara-cytidine sterileinjectable solutions such as in cottonseed oil. peanut oil, and sesameseed oil, or dispersions or sterile non-aqueous solutions or dispersionsin water, aqueous saline solutions or dispersions suited for injectableuse, or sterile powders suited for extemporaneous preparation of sterileinjectable solutions or dispersions can be prepared, using the estercompound of this invention. Such solutions are prepared by incorporatingthe ester compound in the solvent or dispersion medium together withappropriate particle coating agents, surfactants, antibacterial orantifungal agents, isotonic agents and the like. Powders can be preparedby freeze-drying such an appropriately prepared solution or dispersion.Dosage unit forms such as vials and ampules are feasible. The dosagedepends on age, weight, and severity of condition of the subject, routeand frequency of administration, and can vary from 0.1 to about 50mgs./kg., or a daily total dose of about 3 to about 4000 mgs., givensingly or in divided doses. A unit dosage can contain the ester compoundof this invention from about 3 to about 1000 mgs. per unit. This can befrom about 0.5% to 25% w/v of the total composition. Utilizing thesustained release characteristic of the ester compounds of thisinvention, unit doses can be prepared and administered intramuscularlyin amounts varying from about 0.5 to about 10 grams or more totaldosage, or from about 10 to about 50 mgs./kg. of more. The amount ofester compound in such dosage can vary up to that indicated assufficient to aid regression and palliation of the leukemia. Thus a 50mg./kg. dosage can be given once weekly or doses which can be larger canbe administered at wider spaced time intervals.

For oral administration, either solid or fluid unit dosage forms can beprepared. For preparing solid compositions such as tablets, theprincipal active ingredient is mixed with conventional ingredients suchas talc, magnesium stearate, dicalcium phosphate, magnesium aluminumsilicate, calcium sulfate, starch, lactose, acacia, methylcellulose, andfunctionally similar materials as pharmaceutical diluents or carriers.Wafers are prepared in the same manner as tablets, differing only inshape and the inclusion of sucrose or other sweetener and flavor. Intheir simplest embodiment, capsules, like tablets, are prepared bymixing the active compound of the formulation with an inertpharmaceutical diluent and filling the mixture into a hard gelatincapsule of appropriate size. In another embodiment, capsules areprepared by filling hard gelatin capsules with polymer coated beadscontaining the active compound. Soft gelatin capsules are prepared bymachine encapsulation of a slurry of the active compound with anacceptable vegetable oil, light liquid petrolatum or other inert oil.

Fluid unit dosage forms for oral administration such as syrups, elixirs,and suspensions can also be prepared. The water-soluble forms of theactive compound can be dissolved in an aqueous vehicle together withsugar, aromatic flavoring agents and preservatives to form a syrup. Anelixir is prepared by using a hydro-alcoholic (ethanol) vehicle withsuitable sweeteners such as sucrose together with an aromatic flavoringagent. Suspensions can be prepared of the insoluble forms with a syrupvehicle with the aid of a suspending agent such as acacia, tragacanth,methylcellulose and the like.

The process of this invention is generally one of esterification and maybe shown illustratively in the following reactions wherein X is chloroor bromo: ##STR1##

In the above reaction, variations can be made in a number of the stages.For example, the intermediate compound: ##STR2## can be made by reactionof 5'-O-trityl-ara-cytidine with β,β,β-trihaloethoxycarbonyl halide toform the analogous N-derivative, and subsequently removing the tritylgroup by known methods.

The reaction is given illustratively as follows: ##STR3##

5'-O-Trityl ara-cytidine can be used as starting material for thefollowing alternative reactions in which an excess ofβ,β,β-trichloroethoxycarbonyl chloride is used: ##STR4##

In practicing the invention, and as is disclosed in more detail in theforegoing and ensuing description, the process involves use of a novelclass of intermediates having the following structural formula: ##STR5##in wich y=H, trityl or an acyl radical. These intermediates, where y=Hare capable of being transformed into the wide class of esters disclosedin this application, protected as shown at the amino nitrogen. Theesters, too, are intermediates and constitute the compounds of the aboveformula where y=acyl. These ester intermediates are further capable ofbeing transformed by removal of the protective group on the aminonitrogen into the free amino ester product compounds possessing theaforesaid valuable pharmacological properties, as will be seen from thefollowing description and examples.

Alternatively, the primary amino group of ara-cytidine may be protectedfrom concomitant acylation by protonation. This is done by reactingara-cytidine with the acylating agent, for example, an acyl halide oracyl anhydride in the presence of a sufficiently high hydrogen ionconcentration, so that the primary amino group of ara-cytidine isprotected. It has been found in this invention that the amino group insuch amino protected nucleoside species is resistant to conventionalacylation procedures.

In the above equations, of particular value and interest in the generalsense are those in which the substituent acyl is that of an organiccarboxylic acid, ##STR6## in which R can have a wide range of values.For example, R can broadly mean a straight- or branched-chain aliphaticradical containing from 1 to 20 carbon atoms which can be substituted byhalogen, hydroxyl, carboxyl or mercapto groups, a monocyclic or bicyclicaromatic radical of from 6 to 10 carbon atoms, on a cage-typehydrocarbon radical containing from 7 to 20 carbon atoms. R can alsodenote the variety of substituents that are shown in Table I to XI whichfollow.

Representative values of R in the foregoing are: methyl, ethyl, t-butyl,2,2-dimethylpropyl, 1-chloro-2,3-dimethylbutyl, 2,2-dimethylpropyl,1-mercapto-2,2-dimethylpropyl, phenyl, 2-methylphenyl,2,6-dimethylphenyl, 2,4,6-trimethylphenyl, 1-naphthyl, 2-naphthyl,##STR7## and also groups, which, together with the ##STR8## group makeup the acyl group of acids such as glutamic, glutaric, succinic,fumaric, aconitic, itaconic, levulinic, 3,3-dimethylglutaric and other3,3-dialkylglutaric acids and other acids as will be exemplified later.

Of these, of particular application are the classes of N-protectedintermediates wherein ##STR9## in which R'₁ is an aliphatic radical offrom 1 to 20 carbon atoms, an aromatic radical of from 6 to 10 carbonatoms, a cage-type hydrocarbon radical of from 7 to 20 carbon atoms, amonocyclic aliphatic radical of from 4 to 10 carbon atoms, anaraliphatic radical of from 7 to 12 carbon atoms or a monocyclicheterocyclic radical of from 4 to 10 carbon atoms or wherein ##STR10##is the acyl radical of an aliphatic dicarboxylic acid of from 3 to 8carbon atoms. Eliminative removal of the amino-protecting group resultsin the free amino ester product compound corresponding otherwise to theformula immediately above but wherein ##STR11## wherein R₁ is a radicalselected from the group consisting of an aliphatic of from 1 to 20carbon atoms, aromatic of from 6 to 10 carbon atoms, a monocyclicaliphatic of from 4 to 10 carbon atoms, and araliphatic of from 7 to 12carbon atoms or a monocyclic heterocyclic of from 4 to 10 carbon atoms;or wherein ##STR12## is the acyl radical of an aliphatic dicarboxylicacid of 3 to 8 carbon atoms.

One important class of such novel compounds is that wherein theacylating agent used is an acyl halide or an anhydride of an aliphaticacid containing 1 to 18 carbon atoms, such as acetyl chloride oranhydride, isobutyrylbromide or anhydride, caproyl chloride oranhydride, palmityl chloride or anhydride, stearyl chloride oranhydride, lauroyl chloride or anhydride, oleyl chloride or anhydride,myristic chloride or anhydride, isomers thereof and the like.

Another important class of novel compounds of this invention is thatwherein the acyl radical of ##STR13## is that of a dicarboxylicaliphatic acid of from 3 to 8 carbon atoms, such as glutaric,3,3-dialkylglutaric, succinic, itaconic, or fumaric acid, and the like.

In addition to the above, R can also be a substituted amino group inwhich the substituents can be aliphatic, aromatic, heterocyclic orcage-type radical, as illustrated later. R can also be a mercapto groupor an alkylmercapto group, MS- in which M is as illustrated later. Theacyl substituent at 5'-O can also be those to form a carbonate ester asillustrated later.

In addition to carboxyl acyl groups the derivative groups attached tothe 5'-O oxygen of ara-cytidine can be thio-acyl group such as ##STR14##in which M₁, A₁ and B₁, R₂ and R₃ are as will be illustrated later.

The acyl group attached to the 5'-oxygen of ara-cytidine can also bethat of an esterified phosphoric acid such as ##STR15## in which thevalue of R₄ and R₅ can be an aliphatic or substituted aliphatic as willbe illustrated later; ##STR16## in which the value of A₂ and B₂ can behydrogen or aliphatic as will be illustrated later, or ##STR17## inwhich the value of A₂ and B₂ is as given above.

The processes of this invention as described above render possible thepreparation of a wide variety of 5'-O-esters of ara-cytidine. Amongthese products are a number of classes of novel compounds, heretoforeunknown, in their free base or salt form which possess as a commonproperty, the advantage of sustained release previously described.

DETAILED DESCRIPTION OF THE INVENTION

In the following tables there are set forth the acylating agentstogether with the substituent groups of the acylating agents referred toabove and the identification of the product ester of ara-cytidine. Theseagents are reacted with ara-cytidine protected as described above, andin each case the intermediate product containing the N⁴-trihaloethoxycarbonyl protective group is formed, which group issubsequently removed as described above and in the examples with follow.

A number of acylating agents containing the trichloroethoxycarbonylgroup as a substituent are given illustratively in the tables. It is tobe understood that such substituted acylating agents can be prepared byreaction with trichloroethoxycarbonyl chloride as described above (forara-cytidine and related compounds) and as illustrated in the followingexamples. The trichloroethoxycarbonyl groups of such 5'-O-acyl radicalsare removed along with the trihaloethoxycarbonyl group protecting theamino group of ara-cytidine in the final eliminative step of theprocess.

The acid chlorides of the carboxylic acids, used as acylating agents,can be prepared by conventional methods, as for example, by reaction ofthe acid RCOOH (a) with SOCl₂ (b) with PCl₅, or (c) with POCl₃. Themethod (a) is suitable for most acids except those which boil within5°-10° C. of SOCl₂, in which case, the method (c) is suitable.

It is further to be understood that the acid RCOOH can be transformed toan active acylating agency by first reacting it with p-toluenesulfonylchloride, and this reaction product (tosylate) can be used in place ofthe anhydride or chloride, in accordance with the procedures describedin J. Am. Chem. Soc. 77, 6214 (1955).

Analogous to the above acid RCOOH can be transformed to an acylatingagency by first reacting it with (CF₃ CO)₂ O, and then using the productas acylating agent, in accordance with the procedures described in Chem.Rev. 55, 787 (1955).

A further esterification procedure which is suitable is to use the acidRCOOH directly, carrying out the reaction in the presence ofdicyclohexylcarbodiimide, in accordance with the procedures described inCompt. Rend. 252, 896 (1961); Ibid. 255, 945 (1962); J. Org. Chem. 27,4075 (1962) and Tetrahedron 21, 3531 (1965).

For acylation of ara-cytidine only at the 5'-O position, according tothis invention, coincident acylation of the amino group at position 4must be prevented. This is done by first protecting the amino group by asuitable protective agent. In one form of the invention process, this isaccomplished by reacting ara-cytidine with a trihaloethoxycarbonylhalide, in which "halo" is chlorine or bromine, and "halide" ischloride, bromide or iodide. Exemplary reagents aretrichloroethoxycarbonyl chloride (Aldrich Chemical Co., Milwaukee,Wisconsin) and tribromoethoxycarbonyl chloride [J. Org. Chem. 33,3589-93 (1968)].

When ara-cytidine is reacted with the appropriate molar proportion(about 2 ) of trihaloethoxycarbonyl halide, the intermediate productN⁴,5'-O-bis-trihaloethoxycarbonyl ara-cytidine is formed. This reactionis previously shown. The reaction can be carried out in pyridine, andthe product recovered by removal of the solvent by distillation. Thereaction conditions for protective group removal described in Example 1can be followed.

The N⁴, 5'-O-bis-trihaloethoxycarbonyl ara-cytidine can be hydrolyzed bytreatment with dilute sodium hydroxide. The compound dissolved intetrahydrofuran is treated with an equal volume of sodium hydroxidesolution, about 0.3 N, let stand at room temperature to equilibrate, andthen is neutralized with acetic acid. The product, N⁴-trihaloethoxycarbonyl ara-cytidine, can be removed by crystallizationand purified by recrystallization from acetone.

Advantageously, N⁴ -trihaloethoxycarbonyl ara-cytidine can be preparedby reacting 5'-O-trityl ara-cytidine (U.S. Pat. No. 3,338,832,Example 1) with N⁴ -trihaloethoxycarbonyl halide (THEC halide) (Example1). The reaction is conducted in dry pyridine at low temperature, about-5° to 5°, preferably about 3° C. If the molar proportion of 5'-O-tritylara-cytidine to THEC halide is about 1:1, the reaction product is N⁴-trihaloethoxycarbonyl- 5'-O-trityl-ara-cytidine. If an excess of THEChalide is used, i.e., a molar proportion less than 1:3, preferably about1:4 to 1:5, the reaction product is N⁴-2',3'-O-tris-trihaloethoxycarbonyl-5'-O-trityl-ara-cytidine. Thesolvent is removed and the residue is extracted into a chlorinatedhydrocarbon solvent, e.g., methylene chloride, and washed with water. Inthe case where the reaction product istris-trihaloethoxycarbonyl-5'-O-trityl-ara-cytidine, the protectivegroup at 2'-O and 3'-O can be removed at this point, if desired, byhydrolysis with a base, e.g., 0.15 N sodium hydroxide in 50%tetrahydrofuran-50% water, to give the N⁴ -monoprotected 5'-O-tritylproduct which is isolated. Alternatively, the washed residue in achlorinated hydrocarbon solvent is evaporated. If desired, theTHEC-protected, tritylated products can be recrystallized from suitablesolvents, e.g., methylene chloride or acetone. The protectedintermediates, mono- or tris-THEC 5'-O-trityl CA derivatives, aretreated with 80% acetic acid as illustrated in Example 2 to remove the5'-O-trityl group to yield the intermediate, N⁴ -trihaloethoxycarbonylara-cytidine.

By acylation at the 5'-O position by use of the acylating agentsexemplified by Tables I to XI and illustrated in the examples, there areproduced the novel amino protected 5'-O-esters of ara-cytidine of theinvention. The protective group is removable by treatment with metalliczinc in methanol solution of the ester; by treatment with metallic zinc,for example as zinc dust, and acetic acid, for example, in 80 to 90%acetic acid solution; or by treatment with zinc chloride or zinc acetatein methanol.

The water solubility of the 5'-O-derivatives of this invention can beimproved and thus their pharmaceutical versatility is enhanced byconversion to their salt form with pharmaceutically accepted acids whichhave a pK about or less than 2. These acids can be broadly classed asthe strong mineral or organic acids, and this class of acids areappropriate because ara-cytidine and the 5'-O-derivatives of it whichcharacterizes this invention are weak bases. Examples of the strongacids are hydrochloric, sulfuric, phosphoric, glutaric, glutamic,tartaric, trihydroxybenzoic, formic and the like. They are formed bysuspending the desired 5'-O-derivatives in a medium such as methanol andadding appropriately one equivalent of the desired acid. The result is asolution of the acid salt, which can be caused to separate by the addingof appropriate media such as diethyl ether. The salts can be purified byrecrystallization from solvent mixtures such as methanol:ether. Thehydrohalide salt can also be obtained by simply not neutralizing theacylation mixture resulting from the reaction of RCOCl before isolatingthe acylated product from the solvent.

In Table I, below, are given, illustratively, typical acylating agentsand resulting ara-cytidine-5'-O-acylate products for the case when theacyl group is ##STR18## wherein R₁ is as defined previously.

                                      TABLE I                                     __________________________________________________________________________    R of RCO = R.sub.1                                                                              Acylating                                                   No.                                                                              R.sub.1        Agent          Product                                      __________________________________________________________________________    1  CH.sub.3       Acetic anhydride or acetyl                                                                   5'-O-acetyl ara-                                               chloride       cytidine                                     2  (CH.sub.3).sub.3 C                                                                           Pivaloyl chloride                                                                            5'-O-pivaloyl ara-                                                            cytidine                                     3  (CH.sub.3).sub.2 CH                                                                          Isobutyryl chloride                                                                          5'-O-isobutyryl                                                               ara-cytidine                                 4  CH.sub.3 (CH.sub.2).sub.7                                                                    Octanoyl chloride                                                                            5'-O-octanoyl ara-                                             (caproyl chloride)                                                                           cytidine                                     5  CH.sub.3 (CH.sub.2).sub.14                                                                   Palmityl chloride                                                                            5'-O-palmityl ara-                                                            cytidine                                     6  CH.sub.3 (CH.sub.2).sub.16                                                                   Stearyl chloride                                                                             5'-O-stearyl ara-                                                             cytidine                                     7  CH.sub.3 (CH.sub.2).sub.7 CHCH(CH.sub.2).sub.7                                               Oleyl chloride 5'-O-oleyl ara-                                                               cytidine                                         ##STR19##     β-chloropivaloyl chloride                                                               5'-O-(β-chloropi- valoyl) ara-                                           cytidine                                     9                                                                                 ##STR20##     p-nitrobenzoyl chloride                                                                      5'-O-p-nitroben- zoyl ara-cytidine           10                                                                                ##STR21##     o-toluoyl chloride                                                                           5'-O-toluoyl ara- cytidine                   11                                                                                ##STR22##     Benzoyl chloride                                                                             5'-O-benzoyl ara- cytidine                   12                                                                                ##STR23##     2,6-dimethylbenzoyl chloride                                                                 5'-O-(2,6-dimethyl- benzoyl) ara-                                             cytidine                                     13                                                                                ##STR24##     2,4,6-trimethylbenzoyl chloride                                                              5'-O-(2,4,6-tri- methylbenzoyl) ara-cytid                                     ine                                          14                                                                                ##STR25##     1-fluorene carbonyl chloride                                                                 5'-O-(1-fluorene carbonyl)                                                    ara- cytidine                                15                                                                                ##STR26##     9-fluorene carbonyl chloride                                                                 5'-O-(9-fluorene carbonyl)                                                    ara- cytidine                                16                                                                                ##STR27##     1-naphthoyl chloride                                                                         5'-O-(1-naphthoyl) ara-cytidine              17                                                                                ##STR28##     1-indene-carbonyl chloride                                                                   5'-O-1-indene-car- bonyl ara-cytidine        18                                                                                ##STR29##     p-anisoyl chloride                                                                           5'-O-p-anisoyl ara- cytidine                 19                                                                                ##STR30##     3,4,5-trimethoxybenzoyl chloride                                                             5'-O-(3,4,5-tri- methoxybenzoyl) ara-                                         cytidine                                     20                                                                                ##STR31##     p-toluoyl chloride                                                                           5'-O-p-toluoyl ara- cytidine                 21                                                                                ##STR32##     1-norbornanecarbonyl chloride                                                                1-norbornylcarbonyl ara-cytidine             22                                                                                ##STR33##     exo- or exo/endo-mixture of 2-norbornanecarbonyl chlo-                        ride           exo- or exo/endo- mixture of 5'-O-                                            (2-norbornylcar- bonyl)ara-cytidine          23                                                                                ##STR34##     7-norbornane carbonyl chlo- ride                                                             5'-O-(7-norbornye- carbonyl) ara-                                             cytidine                                     24                                                                                ##STR35##     2-adamantane carbonyl chloride                                                               5'-O-2-adamantyl- carbonyl                                                    ara- cytidine                                25                                                                                ##STR36##     1-adamantyl acetyl chloride                                                                  5'-O-(1-adamantyl acetyl) ara- cytidine      26                                                                                ##STR37##     [α-chloro-3,5,7-trimethyl- 1-adamantyl                                  acetyl]chlo- ride                                                                            5'-O-[(α-chloro- 3,5,7-trimethyl-1-                                      adamantyl)acetyl] ara-cytidine              27                                                                                ##STR38##     pentacyclo[4.2.0.0.sup.2,5. 0.sup.3,8.0.sup.4,7 ]octane                       carbonyl chloride (cubane carbonyl chloride)                                                 5'-O-pentacyclo- [4.3.0.0.sup.2,5.                                            0.sup.3,8.0.sup.4,7 ]octyl- carbonyl                                          ara- cytidine                                28                                                                                ##STR39##     cyclobutane carboxylic acid anhydride                                                        5'-O-cyclobutyl- carbonyl ara- cytidine      29                                                                                ##STR40##     cyclopentane carbonyl chloride                                                               5'-O-cyclopentyl- carbonyl                                                    ara- cytidine                                30                                                                                ##STR41##     cyclohexane carbonyl chloride                                                                5'-O-cyclohexyl- carbonyl ara- cytidine      31                                                                                ##STR42##     picolinyl chloride                                                                           5'-O-picolinyl ara-cytidine                  32                                                                                ##STR43##     tetrahydrofuroyl chloride (tetrahydropyromuconyl                              chloride)      5'-O-tetrahydro-2- furoyl ara- cytidine      33                                                                                ##STR44##      9-xanthene carbonyl chloride                                                                5'-O-(9-xanthenyl- carbonyl) ara-                                             cytidine                                     34                                                                                ##STR45##     nicotinyl chloride                                                                           5'-O-nicotinoyl ara-cytidine                 35                                                                                ##STR46##     6-methoxy-4-quinoline carbonyl chloride (quininyl                             chloride)      5'-O-(6-methoxy-4- quinolylcarbonyl)                                          ara-cytidine                                 36                                                                                ##STR47##     4-cinnoline carbonyl chloride                                                                5'-O-(4-cinnolyl- carbonyl) ara-                                              cytidine                                     37                                                                                ##STR48##     2-thiophene carbonyl chloride                                                                5'-O-(2-thenoyl) ara- cytidine               38                                                                                ##STR49##     4-thianaphthene acetyl chloride                                                              5'-O-(4-thianaph- thene acetyl) ara-                                          cytidine                                     39                                                                                ##STR50##     2-furoyl chloride                                                                            5'-O-2-furoyl ara- cytidine                  40                                                                                ##STR51##     5-bromo-2-furoyl chloride                                                                    5'-O-(5-bromo-2- furoyl)                                                      ara- furoyl)ara- cytidine                    41                                                                                ##STR52##     coumalyl chloride                                                                            5'-O-coumalyl ara cytidine                   42                                                                                ##STR53##     coumarin-3-carbonyl chloride                                                                 5'-O-coumarin-3- carbonyl ara- cytidine      43                                                                                ##STR54##     isonicotinoyl chloride                                                                       5'-O-isonicotinoyl ara-cytidine              44                                                                                ##STR55##     2-quinuclidine carbonyl chloride                                                             5'-O-(2-quinuclidi- nylcarbonyl) ara-                                         cytidine                                     45                                                                                ##STR56##     3-quinuclidine carbonyl chloride                                                             5'-O-(3-quinuclidi- nylcarbonyl) ara-                                         cytidine                                     46                                                                                ##STR57##     4-quinuclidine carbonyl chloride                                                             5'-O-(4-quinuclidi- nylcarbonyl) ara-                                         cytidine                                     47                                                                                ##STR58##     N-trichloroethoxycarbonyl- 2-pyrrole carbonyl                                                5'-O-(2-pyrrolylcar- bonyl)                                                   ara-cytidine                                 48                                                                                ##STR59##     N-trichloroethoxycarbonyl- 2-indole carbonyl                                                 5'-O-(2-indolylcar- bonyl) ara-cytidine      49                                                                                ##STR60##     N-trichloroethoxycarbonyl- 3-indole carbonyl                                                 5'-O-(3-indolylcar- bonyl) ara-cytidine      50                                                                                ##STR61##     hydroxybenzoyl chloride trichlorocarbonate                                                   5'-O-hydroxyben- zoyl ara-cytidine           51                                                                                ##STR62##     trans-3-(n-propyl)-hygric acid chloride,                                                     5'-O-trans-[3-(n- propyl)hygroyl]-                                            ara-cytidine                                 52 HOOCCH.sub.2 CH.sub.2                                                                        succinic anhydride                                                                           5'-O-hemisuccinyl                                                             ara-cytidine                                 53                                                                                ##STR63##     fumaryl chloride                                                                             5'-O-hemifumaryl ara-cytidine                54                                                                                ##STR64##     3,3-dimethylglutaric anhydride                                                               5'-O-hemi(3,3-di- methylglutaryl)                                             ara-cytidine                                 55                                                                                ##STR65##     itaconic anhydride                                                                           5'-O-itaconyl ara- cytidine                  56                                                                                ##STR66##     aconitic anhydride                                                                           5'-O-aconityl ara- cytidine                  __________________________________________________________________________     *TCEC means the trichloroethoxycarbonyl radical.                         

In Table II, below, are given typical acylating agents and resultingproducts in the case when the acyl group is ##STR67##

                                      TABLE II                                    __________________________________________________________________________    A         B      Acylating Agent                                                                            Final Product                                   __________________________________________________________________________    H         H      N-carbonylsulfamic acid                                                                    5'-O-(carbamoyl)-ara-cytidine                                    chloride, sodium cyanide                                                      and trifluoro-acetic                                                          acid                                                         H         CH.sub.3 CH.sub.2                                                                    ethyl isocyanate                                                                           5'-O-(ethylcarbamoyl)-ara-                                                    cytidine                                                   ##STR68##                                                                           cyclohexyl isocyanate                                                                      5'-O-(cyclohexylcarbamoyl)-  ara-cytidine       H         CH.sub.3 (CH.sub.2).sub.7                                                            n-octyl isocyanate                                                                         5'-O-(n-octylcarbamoyl)-                                                      ara-cytidine                                    C.sub.2 H.sub.5                                                                         C.sub.2 H.sub.5                                                                      diethylamine and                                                                           5'-O-(diethylcarbamoyl)ara-                                      phosgene     cytidine                                        n-C.sub.4 H.sub.9                                                                       n-C.sub.4 H.sub.9                                                                    di-n-butylamine and                                                                        5'-O-(di-n-butylcarbamoyl)-                                      phosgene     ara-cytidine                                    CH.sub.2CHCH.sub.2                                                                      ○                                                                             N-allylaniline and                                                                         5'-O-(N-allyl-N-phenylcar-                                       phosgene     bamoyl)-ara-cytidine                                             pipyridine + phos-                                                                         5'-O-(N,N-pentamethylene-                                        gene         carbamoyl)-ara-cytidine                         (pentamethylene)                                                              __________________________________________________________________________

In the foregoing formula, A and B are the same or different radicalsselected from the group consisting of H, aliphatic of from 1 to 10carbon atoms, monocyclic aliphatic of from 4 to 10 carbon atoms, andaromatic of from 6 to 10 carbon atoms, or in which A and B together makeup an aliphatic chain of from 3 to 6 carbon atoms.

In the case where R of RCO = MS, general procedures for preparing thesubstituted monothiol chlorocarbonates as acylating agents are given inJ. Am. Chem. Soc. 82, 4347 (1960) and Monatsch. Chem. 81, 939 (1950).Briefly the mercaptan MSH is reacted with COCl₂ in the presence of NiCl₃to produce the acylating agent ##STR69## In this class M is a radicalselected from the group consisting of aliphatic of from 1 to 10 carbonatpms, monocyclic aliphatic of from 4 to 10 carbon atoms, and aromaticof from 6 to 10 carbon atoms, and aralkyl from 7 to 12 carbon atoms.Representative acylating agents of this kind and the resulting finalproducts are:

                                      TABLE III                                   __________________________________________________________________________              Mercaptan Reagent                                                   M         (+COCl.sub.2)                                                                            Final Product                                            __________________________________________________________________________     ##STR70##                                                                              benzyl mercaptan                                                                         ara-cytidine 5'-S-benzylthiocar-  bonate                 (CH.sub.3).sub.2 CH                                                                     isopropyl mercaptan                                                                      ara-cytidine 5'-S-isopropylthio-                                              carbonate                                                CH.sub.3 (CH.sub.2).sub.3                                                               n-butyl mercaptan                                                                        ara-cytidine 5'-S-n-butylthio-                                                carbonate                                                CH.sub.2CHCH.sub.2                                                                      allyl mercaptan                                                                          ara-cytidine 5'-S-allylthiocar-                                               bonate                                                    ##STR71##                                                                              benzenethiol                                                                             ara-cytidine 5'-S-phenylthiocar-  bonate                  ##STR72##                                                                              pentachlorothiophenol                                                                    ara-cytidine 5'-S-pentachloro-  phenylthiocarbonate       ##STR73##                                                                              cyclohexylmercaptan                                                                      ara-cytidine 5'-S-cyclohexylthio-  carbonate             CH.sub.3 (CH.sub.2).sub.9                                                               n-decyl mercaptan                                                                        5'-ara-cytidine 5'-S-n-decylthio-                                             carbonate                                                __________________________________________________________________________

Where the acyl radical attached to the 5' oxygen of ara-cytidine is##STR74## the acylating agent can be prepared in a manner analogous tothe above, substituting thiophosgene (CSCl₂) for CDCl₂. In this class M₁is a radical selected from the group consisting of aliphatic of from 1to 10 carbon atoms, aromatic of from 6 to 10 carbon atoms, andaraliphatic of from 7 to 12 carbon atoms. Representative acylatingagents of this kind and the resulting final products are:

                  TABLE IV                                                        ______________________________________                                                   Mercaptan Reagent                                                  M.sub.1    (+ CSCl.sub.1) Final Product                                       ______________________________________                                        C.sub.2 H.sub.5                                                                          ethyl mercaptan +                                                                            ara-cytidine 5'-                                               thiophosgene   S-ethyl xanthate                                     ##STR75## phenyl thiol + thiophosgene                                                                  ara-cytidine 5'- S-phenyl xanthate                   ##STR76## benzyl thiol + thiophosgene                                                                  ara-cytidine 5'- benzyl xanthate                    CH.sub.3 (CH.sub.2).sub.9                                                                decyl thiol +  5'-ara-cytidine                                                thiophosgene   5'-S-decyl xan-                                                               thate                                               ______________________________________                                    

Where the acyl radical attached to the 5'-oxygen of ara-cytidine is##STR77## the preparation is by the reaction of the class of products ofTable IV, (i.e., where the acyl radical attached to the 5'-oxygen ofara-cytidine is ##STR78## with A₁ B₁ NH. General procedures for carryingout this reaction are given in J. Chem. Soc., 2195 (1951). In this classA₁ and B₁ are the same or different radicals selected from the groupconsisting of H, alkyl of from 1 to 7 carbon atoms, and aromatic of from6 to 10 carbon atoms.

Representative compounds involved in this method are:

                                      TABLE V                                     __________________________________________________________________________    R.sub.1                                                                             R.sub.2                                                                             Reagent   Final Product                                           __________________________________________________________________________    H     H     ammonia   5'-O-(thiocarbamoyl)ara-cytidine                        CH.sub.3                                                                            H     methyl amine                                                                            5'-O-(methyl thiocarbamoyl)ara-                                               cytidine                                                C.sub.2 H.sub.5                                                                     H     ethyl amine                                                                             5'-O-(ethyl thiocarbamoyl)ara-                                                cytidine                                                CH.sub.3                                                                            CH.sub.3                                                                            dimethyl amine                                                                          5'-O-(dimethyl thiocarbamoyl)ara-                                             cytidine                                                C.sub.2 H.sub.5                                                                     C.sub.2 H.sub.5                                                                     diethyl amine                                                                           5'-O-(diethyl thiocarbamoyl)ara-                                              cytidine                                                 ##STR79##                                                                          CH.sub.3                                                                            N-methyl aniline                                                                        5'-O-(methylphenylthiocarbamoyl)-                       __________________________________________________________________________                          ara-cytidine                                        

Where the acyl radical attached to the 5'-oxygen of ara-cytidine is##STR80## the preparation is analogous to that of using the carboxylicacid chlorides, but using the appropriate sulfonyl chloride. In thisclass R₂ is a radical selected from the group consisting of alkyl offrom 1 to 7 carbon atoms, aromatic of from 6 to 10 carbon atoms, andsubstituted aromatic of from 6 to 12 carbon atoms. Representativeacylating agents and final products are:

                                      TABLE VI                                    __________________________________________________________________________     ##STR81##                                                                    R.sub.2       Acylating Agent                                                                             Final Product                                     __________________________________________________________________________    CH.sub.3      methanesulfonylchloride                                                                     5'-O-methylsulfonyl-ara-                                                      cytidine                                           ##STR82##    benzenesulfonyl chloride                                                                    5'-O-phenylsulfonyl-  ara-cytidine                 ##STR83##    p-bromobenzenesulfonyl chloride                                                             5'-O-(p-bromophenylsul-  fonyl)ara-cytidine        ##STR84##    p-nitrobenzenesulfonyl chloride                                                             5'-O-(p-nitrophenylsul- fonyl)ara-cytidine         ##STR85##    p-toluenesulfonyl chloride                                                                  5'-O-(p-tolylsulfonyl)- ara-cytidine               ##STR86##    2,4,6-triisopropylbenzenesul- fonyl chloride                                                5'-(2,4,6-triisopropyl- phenylsulfonyl)ara-                                   cytidine                                          __________________________________________________________________________

Where the acyl radical attached to the 55'-oxygen of ara-cytidine is##STR87## the preparation of the acylating agent is by the known methodof reacting ROH with SOCl₂ to produce the acylating agent ##STR88##which is then used analogously to the carboxylic acid chlorides. In thisclass R₃ is a radical selected from the group consisting of aliphatic offrom 1 to 20 carbon atoms, aromatic of from 6 to 10 carbon atoms, andaraliphatic of from 7 to 12 carbon atoms. Representative compoundsinvolved are:

                  TABLE VII                                                       ______________________________________                                         ##STR89##                                                                                Reagent                                                           R.sub.3     (+SOCl.sub.2) Final Product                                       ______________________________________                                        H           sulfur trioxide                                                                             ara-cytidine                                                                  5'-sulfate                                          CH.sub.3    methanol + thi-                                                                             ara-cytidine                                                    onyl chloride 5'-methyl sul-                                                                fate                                                C.sub.2 H.sub.5                                                                           ethanol + thi-                                                                              ara-cytidine                                                    onyl chloride 5'-ethyl sul-                                                                 fate                                                 ##STR90##  phenol + thio- nyl chloride                                                                 ara-cytidine 5'-phenyl sul- fate                     ##STR91##  benzyl alcohol + thionyl chloride                                                           ara-cytidine 5'-benzyl sul- fate                    n-CH.sub.3 (CH.sub.2).sub.17                                                              n-octadecyl al-                                                                             ara-cytidine                                                    cohol + thionyl                                                                             5'-octadecyl                                                    chloride      sulfate                                             ______________________________________                                    

Where the acyl radical attached to the 5'-oxygen of ara-cytidine is##STR92## the preparation of the acylating agent can be carried out byknown methods. General procedures using an aliphatic alcohol incombination with dicyclohexylcarbodiimide and phosphorus oxychloride(POCl₃) are described is J. Am. Chem. Soc. 80, 6212 (1958). Generalprocedures using di-substituted (R₄ and R₅) phosphorchloridates asacylating agents are described in Angew. Chem. Internat. Edit. 6, 362(1967). General procedures using substituted phosphates (R₄) anddicyclohexylcarbodiimide are described in Chem. Ber. 100, 2228 (1967).In this class R₄ and R₅ are the same or different radicals selected fromthe group consisting of alkyl of from 1 to 7 carbon atoms and haloalkylof from 1 to 7 carbon atoms. Representative compounds involved are:

                                      TABLE VIII                                  __________________________________________________________________________     ##STR93##                                                                    R.sub.4                                                                              R.sub.5                                                                              Reactants     Final Products                                    __________________________________________________________________________    H      CCl.sub.3 CH.sub.2                                                                   β,β,β-trichloroethylphos-                                                    β,β,β-trichloroethyl-                            phate + DCC   (5'-ara-cytidylate)                               CH.sub.3 CH.sub.2                                                                    CH.sub.3 CH.sub.2                                                                    diethylphosphoro chloridate                                                                 diethyl-(5'-ara-cytidyl-                                                      ate)                                              CCl.sub.3 CH.sub.2                                                                   CCl.sub.3 CH.sub.2                                                                   bis-β,β,β-trichloroethyl-                                                    bis-β,β,β-trichloroethyl-                        phosphoro chloridate                                                                        5'-ara-cytidylate)                                __________________________________________________________________________

Where the acyl radical attached to the 5'-oxygen of ara-cytidine is##STR94## the acylating agent is ##STR95## and the acylation is carriedout following known procedures for the preparation of carbonate esters.In this class R₆ is a radical selected from the group consisting ofaliphatic of from 1 to 20 carbon atoms, aromatic of from 6 to 10 carbonatoms, and araliphatic of from 7 to 12 carbon atoms. Representativecompounds are:

                  TABLE IX                                                        ______________________________________                                         ##STR96##                                                                    R.sub.6     Reagent        Product                                            ______________________________________                                        CH.sub.3    methyl chloro- ara-cytidine 5'-                                               formate        methyl carbonate                                   C.sub.2 H.sub.5                                                                           ethyl chloro-  ara-cytidine 5'-                                               formate        ethyl carbonate                                     ##STR97##  carbobenzoxy chloride                                                                        ara-cytidine 5'- phenyl carbonate                  CH.sub.3 (CH.sub.2).sub.7                                                                 octyl chloro-  octanyl (5'-ara-                                               formate        cytidylyl)carbo-                                                              nate                                               CH.sub.3 (CH.sub.2).sub.15                                                                hexadecyl chloro-                                                                            ara-cytidine 5'-                                               formate        hexadecyl carbo-                                                              nate                                                ##STR98##  phenyl chloro- formate                                                                       ara-cytidine 5'- phenyl carbonate                  ______________________________________                                    

Where the acyl radical attached to the 5'-oxygen of ara-cytidine is##STR99## the final product is prepared by reacting the intermediatecompound, produced as described above in connection with Table VIII, N⁴-trichloroethoxycarbonyl-ara-cytidine-5'-phosphate, with the appropriateamine compound in the presence of dicyclohexylcarbodiimide. Generalanalogous procedures are described in J. Am. Chem. Soc. 80, 3752 (1958).In this class A₂ and B₂ are the same or different radicals selected fromthe group consisting of H and alkyl of from 1 to 7 carbon atoms.Representative compounds involved are:

                                      TABLE X                                     __________________________________________________________________________     ##STR100##                                                                   A.sub.2                                                                            B.sub.2                                                                            Amine        Final Product                                          __________________________________________________________________________              (NTCEC)                                                             H    H                                                                                   ##STR101##  ara-cytidine 5'-phosphoramidate                        CH.sub.3                                                                           H    | + || + methyl amine                                           ara cytidine 5'-(methyl phosphor-                                             amidate)                                               C.sub.2 H.sub.5                                                                    H    | + || + ethyl amine                                            ara-cytidine 5'-(ethyl phosphor-                                              amidate)                                               CH.sub.3                                                                           CH.sub.3                                                                           | + || + dimethyl amine                                         ara-cytidine 5'-(dimethyl phos-                                               phoramidate)                                           C.sub.2 H.sub.5                                                                    C.sub.2 H.sub.5                                                                    1 + || + diethyl amine                                                   ara-cytidine 5'-(diethyl phos-                                                phoramidate)                                           __________________________________________________________________________     | = N.sup.4 -trichloethoxycarbonyl-ara-cytidine                      || = DCC = dicyclohexylcarbodiimide                    

Where the acryl radical attached to the 5'-oxygen of ara-cytidine is##STR102## the acylating agent is prepared in accordance with J. Am.Chem. Soc. 88, 4292 (1966), and with Angew. Chem. Internal. Edit. 6, 362(1967), previously referred to in connection with Table VIII. In thisclass A₂ and B₂ have the meanings given above with respect to Table X.Representative compounds involved are:

                                      TABLE XI                                    __________________________________________________________________________     ##STR103##                                                                   __________________________________________________________________________    A.sub.2                                                                            B.sub.2                                                                            Acylating Agent                                                                              Final Product                                        __________________________________________________________________________    H    C.sub.2 H.sub.5                                                                    ethyl dichlorothiophosphate                                                                  ara-cytidine 5'-(o-ethyl-                                                     phosphorothioate)                                    C.sub.2 H.sub.5                                                                    C.sub.2 H.sub.5                                                                    diethyl dichlorothiophosphate                                                                ara-cytidine 5'-(o,o-di-                                                      ethyl phosphorothioate)                              H    H    triimidazolyl 1-phosphinsul-                                                                 ara-cytidine 5'-phosphoro-                                     fide           thioate                                              __________________________________________________________________________

We have discovered a further method for the preparation of the 5'-estersdescribed in this invention without resort to a special blocking groupfor the amino function. The alternate route takes advantage of the factthat when the amino group is protonated it is unreactive towardacylating agents. Thus, we simply use the proton as the blocking group,reacting a suitably activated acid, such as an acid chloride oranhydride, with an acid salt, such as the hydrochloride salt, of thenucleoside.

As an example, one equivalent of palmityl chloride is allowed to reactat room temperature with a solution of ara-cytidine hydrochloride indimethylacetamide or dimethylformamide. After a few hours, thin layerchromatography shows that the main product is 5'-O-palmitylara-cytidine, with small amounts of diesterified products. The solventis evaporated in vacuo, and the oil is converted to a solid bytrituration with aqueous bicarbonate. The solid is collected on a filterand washed with water, pressed dry, and washed thoroughly with ethylacetate to remove impurities. The resulting product, obtained in betterthan 50% yield, shows a single, ultraviolet-absorbing spot on thin layerchromatography and is essentially analytically pure.

The method is applicable to all nucleosides bearing an amino group, suchas nucleosides of adenine and guanine. The acyl moiety includes that ofany acid that can be suitably activated, for example by the formation ofan acid chloride, anhydride, or mixed anhydride, such that it can forman ester bond with an alkyl hydroxyl group but is unreactive towards aprotonated amino group. The 5'-O-acyl derivatives of ara-cytidinedescribed in the preceding discussions as made by the N⁴-trihaloethoxycarbonyl-protected method, and illustrated in the aboveTables I to XI, can also be made by the proton-protected route. Theacylating agents used in the N⁴ -trihaloethoxycarbonyl-protected methodand exemplified in Tables I to XI are applicable in the proton-protectedroute.

The proton-protected process is illustrated in Examples 24 to 32.

EXAMPLE 1 Preparation of N⁴ -trichloroethoxycarbonyl-5 -O-tritylara-cytidine ##STR104##

A 193.69 g. (.40M) sample of 5'-O-trityl ara-cytidine is dissolved in 4l. of freshly distilled anhydrous pyridine. The solution is cooled to 3°and treated with 84.4 g. (.40M) of trichloroethoxycarbonyl chloride. Thesolution is stirred at 3° for 4 hours and then allowed to come to 25°over ca. 18 hours. The pyridine is distilled at 40° in vacuo and thegummy residue treated with 1 l. of methylene chloride. A solid (23.7 g.)separated and is removed by filtration. Thin layer chromatography (TLC)shows the material to be starting material. The methylene chloridesolution is washed 3 times with 0.1 N hydrochloric acid and once withsaturated salt solution. After drying over sodium sulfate the methylenechloride is allowed to slowly evaporate, whereupon crystals aredeposited. The crystals are collected by filtration, washed with coldmethylene chloride and dried giving 64.5 g. of desired product. TLC ofthe methylene chloride mother liquors show spots moving faster than theproduct which are probably materials acylated at 2' and 3' position.These are hydrolyzed by treating the mother liquor residue with 1 l. oftetrahydrofuran and 1 l. of 0.3 N sodium hydroxide. After 1.5 hours allthe faster moving TLC spots have disappeared. The reaction is acidifiedto pH 6.5 with concentrated hydrochloric acid. The tetrahydrofuran isdistilled in vacuo and the aqueous residue extracted with methylenechloride. The methylene chloride is washed and dried as above and againset out to evaporate. Again crystals are deposited. These are collectedand washed giving 42.5 g. of product. The mother liquors are evaporatedfurther and deposit another 45.5 g. of material which this time is about50--50 product and starting material as seen by TLC. The 45.5 g. isheated with 500 ml. of acetone and the residual material removed byfiltration. This is found to be trityl ara-cytidine. The acetone motherliquors are evaporated to dryness and crystallized from methylenechloride by slow evaporation giving 19 g. of product. The total yield isthus 126 g. of product or 48% of theory. A sample is prepared foranalyses by crystallizing it twice from methylene chloride.

Anal. Calcd. for C₃₁ H₂₈ Cl₃ N₃ O₇ :

C, 56.30; H, 4.27; Cl, 16.11; N, 6.36.

Found: C, 56.46; H, 4.30; Cl, 15.25; N, 7.26.

Ultraviolet Spectrum [λ_(max) ^(EtOH) mμ (ε × 10⁻³)]: 232 (11.8), 296(5.38).

infrared Spectrum (γ mull): 3380, 3200, 3120 sh. 1765, 1650, 1620, 1570,1505, 1330, 1245, 1200, 1100 m, 1085, 1065, 810, 785, 770, 750, 740, 715and 705.

EXAMPLE 2 Preparation of N⁴ -trichloroethoxycarbonyl ara-cytidine##STR105##

A 116.2 g. (.175 M) quantity of N⁴ -trichloroethoxycarbonyl-5' -O-tritylara-cytidine is treated with 1 l. of 80% (V/V) acetic acid for 48 hoursat 25°. The mixture deposits crystalline trityl containing materialduring this period which is removed by filtration. The filtrate isevaporated to dryness in vacuo and the last traces of acid removed bycodistillation in vacuo with several portions of ethanol. The glassyresidue is crystallized from ethanol giving 62.5 g. of product. Thesematerials are found by NMR analysis to contain between 10 and 15% oftriphenylmethylcarbinol and/or its ethyl ether. The compound is purifiedfor analysis by chromatography on silica gel, eluting withcyclohexane-ethyl acetate-ethanol (5:3:1) and subsequent crystallizationfrom methylene chloride.

Anal. Calcd. for C₁₂ H₁₄ Cl₃ N₃ O₇ : C, 34.43; H, 3.37; Cl, 25.41; N,10.04.

Found: C, 34.59; H, 3.61; Cl, 24.82; N, 9.99.

Infrared Spectrum (γ_(cm).spsb.-i_(mull) ): 3400, 1765, 1640, 1575,1510, 1330, 1275, 1235, 1195, 1120, 1105, 1070, 1055, 1035, 810, 745.

Ultraviolet Spectrum [λ_(max) ^(EtOH) (ε × 10⁻³)]: 212 (21.8), 239(14.5), 296 (8.3).

EXAMPLE 3 Preparation of 5' -O-pivaloyl-N⁴ -trichloroethoxycarbonylara-cytidine ##STR106##

A 4.18 g. (10 millimole) sample of N⁴ -trichloroethoxycarbonylara-cytidine is dissolved in 50 ml. of freshly distilled anhydrouspyridine. The solution is treated dropwise with 1.32 g. (1.4 ml., 11millimoles) of pivaloyl chloride in 10 ml. of pyridine at 25°. TLC[silica gel; cyclohexane-ethyl acetate-ethanol (5:3:1)] indicates thereaction has not progressed significantly after 48 hours. Thus, another1.32 g. (11 millimoles) of pivaloyl chloride in 10 ml. pyridine is addedand then reaction allowed to stand yet 24 hours longer. TLC indicatesthat little if any of the starting material remains. The reactionmixture is poured into 60 ml. of water and the mixture evaporated todryness in vacuo. The last traces of pyridine are removed bycodistillation several times with toluene in vacuo. The residue isdissolved in chloroform and washed with water, saturated sodium chlorideand dried over sodium sulfate. The chloroform is distilled in vacuo andthe residue crystallized from acetone giving 1.75 g. of product.

In place of pivaloyl chloride pivaloyl anhydride can be used as thepivaloylating agent in the above sample.

In place of pivaloyl chloride there can be substituted isobutyrylchloride or β-chloropivaloyl chloride, thus producing, respectively, 5'-O-isobutyryl-N⁴ -trichloroethoxycarbonyl ara-cytidine and 5' -O-β-chloropivaloyl-N⁴ -trichloroethoxycarbonyl ara-cytidine.

EXAMPLE 4 Preparation of 5' -O-pivaloyl ara-cytidine ##STR107##

A 1.50 g. (3.0 millimole) sample of 5' -O-pivaloyl-N⁴-trichloroethoxycarbonyl ara-cytidine is treated with 25 ml. of 90%(V/V) acetic acid and 2.0 g. (31 millimoles) of zinc dust and themixture stirred ca. 18 hours at 25°. The reaction mixture is thenfiltered and the filtrate evaporated to dryness in vacuo. The residue ischromatographed on 200 g. of silica gel packed and eluted withcyclohexaneethyl acetate-ethanol (5:3:1). The first forty 100 ml.fractions contain none of the desired product, so a switch is made tothe solvent system, methyl ethyl ketone-acetonewater (72:20:8).Fractions 1-18 are combined and evaporated to dryness. Crystallizationof the residue from methanol gives 715 mg. of product, m.p. 255° (dec.).Like results are obtained substituting for the starting material, 5'-O-isobutyryl-N⁴ -trichloroethoxycarbonyl ara-cytidine and 5'-O-β-chloropivaloyl-N⁴ -trichloroethoxycarbonyl ara-cytidine producing,respectively, 5' -O-isobutyryl ara-cytidine and 5'-O-β -chloropivaloylara-cytidine.

In place of pivaloyl chloride in Example 3, benzoyl chloride can besubstituted to provide 5' -O-benzoyl-N⁴ -trichloroethoxycarbonylara-cytidine which can be substituted in the process of Example 4 aboveto provide 5' -O-benzoyl ara-cytidine.

EXAMPLE 5 Preparation of 5' -O-benzoyl cytosine arabinosidehydrochloride

5' -O-benzoyl cytosine arabinoside (65 g.) is dissolved in 250 ml.methanol with the aid of 19 ml. concentrated hydrochloric acid. Ether(500 ml.) is added to opalescence. The hydrochloride rapidlycrystallizes. It is collected, washed with methanol-ether (1:2), ether,and dried, weight 60.5 g., m.p. 204°-205° dec. Ether is added to themother liquor to opalescence. The second crop is collected, washed withether, and dried, weight 6.5 g. (total yield 67 g., 98.5%), m.p.200°-201° dec.

EXAMPLE 6 Preparation of 5' -O-palmityl ara-cytidine ##STR108##

A 4.18 g. (10 millimoles) sample of N⁴ -trichloroethoxycarbonylara-cytidine is dissolved in 50 ml. of anhydrous redistilled pyridineand treated dropwise at room temperature with 3.0 g. (11 millimoles) ofpalmityl chloride dissolved in 10 ml. of methylene chloride. Afterstanding 18 hours 25°, the reaction mixture is poured into 60 ml. ofwater and the solvent distilled in vacuo until about 10 ml. remains. Asemisolid separates and is obtained by decantation followed by washingwith water. The resultant mass is crystallized from methanol giving 5.5g. of material that is presumed to be 5' -O-palmityl-N⁴-trichloroethoxycarbonyl ara-cytidine on the basis of its conversion tothe desired product. This material is dissolved in 100 ml. of 90% aceticacid and treated with 10 g. of zinc dust. The reaction is stirred for 6hours at 25°. The zinc remaining is removed by filtration and thefiltrate evaporated to dryness in vacuo. The last traces of acetic acidare removed by repeated codistillation in vacuo with ethanol. Theresidue is then chromatographed on 100 g. of silica gel, packed andeluted with cyclohexane-ethyl acetate-ethanol (5:3:1). After taking ten100 ml. fractions, the solvent is switched to methyl ethylketone-acetone-water (72:20:8) and another ten 100 ml. fractions taken.Fractions 14-20 are combined and evaporated to dryness. The residue iscrystallized from methanol giving 870 mg. of product, m.p. 139°-141°. Asample is submitted for analysis after two further crystallizations frommethanol, m.p. 143° -146°.

Anal. Calcd. for C₂₅ H₄₃ N₃ O₆ : C, 62.34; H, 9.00; N, 8.72

Found: C, 62.86; H, 9.19; N, 8.47, 8.72.

Ultraviolet Spectrum [λ_(max) ^(EtOH) mμ (ε × 10⁻³)]: 273 (8.30).

Infrared Spectrum (γ_(cm).spsb.-1^(mull)): 3430, 3330, 3280 sh, 1740,1665 sh, 1635, 1600, 1535, 1495, 1485, 1290, 1255, 1195, 1175, 1110,1095, 1040, 860, 790, 785, 780.

NMR Spectrum: Supports proposed structure.

EXAMPLE 7 Preparation of 5' -O-palmityl cytosine arabinosidehydrochloride

5'-palmityl cytosine arabinoside, 55 g. (0.114 mole) is dissolved in amixture of 350 ml. methanol and 10.5 ml. concentrated hydrochloric acid.The solution is diluted with ether until crystallization ensues, andthen further diluted to 4 liters with ether. The crystallinehydrochloride is collected, washed with ether, and dried. Yield 53.8 g.(91%), m.p. 180°-182°.*

EXAMPLE 8 Preparation of 5' -O-octanoyl ara-cytidine ##STR109##

A 4.18 g. (10 millimoles) sample of N⁴ -trichloroethoxycarbonylara-cytidine is dissolved in 50 ml. of anhydrous redistilled pyridineand resultant solution treated dropwise with a solution of 1.8 g. (11millimoles) of octanoyl chloride in 10 ml. of methylene chloride. Thereaction mixture is stirred for 18 hours at room temperature and thenpoured into 60 ml. of water. The solvent is reduced in volume to about10 ml. by distillation in vacuo. The mother liquors are decanted fromthe solid which separates. The solid is washed with water, filtered,dried and crystallized from methanol giving 3.5 g. of 5' -O-octanoyl-N⁴-trichloroethoxycarbonyl ara-cytidine. This material is dissolved in 50ml. of 90% acetic acid and the solution is treated with 5 g. of zincdust. After the reaction mixture has shaken 5 hours at 25°, the residuezinc solids are removed by filtration and the filtrate evaporated todryness in vacuo. The last traces of acetic acid are removed byredistillation in vacuo with several portions of ethanol. The residue ischromatographed on 100 g. of silica gel, packed and eluted with methylethyl ketone-acetone-water (72:20:8). Fractions of 100 ml. volume arecollected. Fractions 4-8 are combined and evaporated to dryness. Theresidue is crystallized from methanol giving 1.2 g. of product, m.p.161.5°-162.5°. A sample is submitted for analyses after anothercrystallization from aqueous methanol, m.p. 124°-125°. The melting pointchange apparently reflects a change in the state of hydration or changein crystal structure since TLC indicates the material to be unchanged.

Anal. Calcd. for C₁₇ H₂₇ N₃ O₆.H₂ O: C, 52.69; H, 7.55; N, 10.85

Found: C, 52.81; H, 7..97; N, 11.32.

Ultraviolet Spectrum [λ_(max) ^(EtOH) mμ (ε × 10⁻³)]: 274 (8.15).

Infrared Spectrum (γ_(cm).spsb.-1^(mull)): 3530, 3480, 3450, 3390, 3320,3280, 3210, 1725, 1710, 1655, 1630, 1530, 1490, 1280, 1240, 1195, 1175,1130, 1115, 1100, 1090, 1050, 1040, 810, 780.

NMR Spectrum: Supports proposed structure.

The procedures of Examples 5-6 can be followed, substituting stearylchloride and oleyl chloride for the acylating agents of the examples,producing, respectively, 5'-O-stearyl ara-cytidine and 5'-O-oleylara-cytidine.

EXAMPLE 9 Preparation of 5'-O-acetyl ara-cytidine ##STR110##

A 4.18 g. (10 millimoles) sample of N⁴ -trichloroethoxycarbonylara-cytidine is dissolved in 50 ml. of anhydrous freshly distilledpyridine. The resultant solution is treated dropwise with 1.03 g. (10millimoles) of acetic anhydride. The reaction mixture is stirred at 25°for 18 hours, then poured into 60 ml. of water and evaporated todryness. The residue is chromatographed on 100 g. of silica gel andeluted with cyclohexane-ethyl acetate-ethanol (5:3:1). The fractionscontaining the material with an Rf only slightly faster than thestarting material are combined and evaporated to dryness.Crystallization of the residue gives 1.05 g. of material presumed to be5-O-acetyl-N⁴ -trichloroethoxycarbonyl ara-cytidine on the basis of itssubsequent conversion to 5'-O-acetyl ara-cytidine. This material isdissolved in 50 ml. of 90% (V/V) acetic acid and the solution treatedwith 1.0 g. of zinc dust. The reaction mixture is shaken for 6 hours at25°. The zinc solids remaining are then removed by filtration and thefitrate evaporated to dryness in vacuo. The residual gum is freed fromtraces of acetic acid by codistillation in vacuo with several portionsof ethanol. The residue is chromatographed on 100 g. of silica gel,packed and eluted with cyclohexaneethyl acetate-ethanol (5:3:1). Thesolvent is switched to methyl ethyl ketone-acetone-water (72:20:8). Thefractions containing the desired product are combined and evaporated todryness. The material is thus rechromatographed on 50 g. of silica gelas described above. The fraction from this column containing the desiredmaterial are combined and evaporated to dryness. The residue iscrystallized from aqueous methanol-benzene giving 300 mg. of product,m.p. 115°-117.5°.

Anal. Calcd. for C₁₁ H₁₅ N₃ O₆.1/2 H₂ O: C, 44.90; H, 5.48; N, 14.28.

Found: C, 45.13; H, 5.95; N, 14.55.

Ultraviolet Spectrum [λ _(max) ^(etOH) mμ (ε × 10⁻³)]: 273 (8.65).

Infrared Spectrum (γ_(cm).spsb.-1.sup. mull): 3400, 3340, 3210, 1745,1660 sh, 1640, 1610, 1535, 1490, 1280, 1255 sh, 1245, 1230, 1105, 1080,1070, 1050, 810, 780, 690.

NMR Spectrum: Suports proposed structure.

EXAMPLE 10 Preparation of 5'-O-(2,4,6-trimethylbenzoyl) ara-cytidine.##STR111##

A 4.18 g. (10 millimoles) sample of N⁴ -trichloroethoxycarbonylara-cytidine is dissolved in 50 ml. of anhydrous redistilled pyridineand the resultant solution treated dropwise with 2.0 g. (11 millimoles)of 2,4,6-trimethylbenzoyl chloride dissolved in 10 ml. of methylenechloride. After 3 days at 25°, TLC indicates that starting material isstill present. Thus, another 2.0 g. of 2,4,6-trimethylbenzoyl chlorideis added and the reaction allowed to stand another 24 hours at 25°. Thereaction mixture is then poured into water and evaporated to dryness invacuo. Th residue is chromatographed on 100 g. of silica gel. Theproduct is eluted with methanol-benzene (5:95). The fractions containingthe material with Rf only slightly faster than the starting material arecombined and evaporated to dryness. The residue is crystallized frommethanol giving 2.0 g. of material presumed to be N⁴-trichloroethoxycarbonyl-5'-O-(2,4,6-trimethylbenzoyl) ara-cytidine onthe basis of its conversion to 5'-O-trimethylbenzoyl ara-cytidine, m.p.122°-125° (dec.). This material is dissolved in 50 ml. of 90% (V/V)acetic acid. The solution is treated with 2 g. of zinc dust and shakenfor 6 hours. The zinc containing solids are filtered from the reactingmixture and the filtrate evaporated to dryness in vacuo. The residue ischromatographed on 100 g. of silica gel, eluting with mixtures ofmethanol benzene (5:95) to pure methanol. The desired material is foundin the methanol fractions, which are then combined and evaporated todryness. The residue is crystallized from methanol giving 670 mg. of5'-O-(2,4,6-trimethylbenzoyl) ara-cytidine, m.p. 252°-253° (dec.). Asample crystallized once more from methanol is submitted for analysis,m.p. 255°-256° (dec.).

Anal. Calcd. for C₁₉ H₁₃ N₃ O₆.1/2 H₂ O: C, 57.28; H, 6.07; N, 10.55.

Found: C, 57.15; H, 6.34; N, 10.86.

Ultraviolet Spectrum [λ _(max) ^(EtOH) m.sub.μ (ε × 10⁻³)]: 273 (9.40).

Infrared Spectrum (γ_(cm).spsb.-1^(mull)): 3430 sh, 3400, 3340, 3280,3210, 3120, 1720, 1695, 1655, 1635, 1625, 1535, 1490, 1285, 1175, 1120,1115, 1095, 1070, 1055, 810, and 780.

NMR Spectrum: Supports proposed structure.

The use as acylating agent of p-nitrobenzoyl chloride, o-toluoylchloride, benzoyl chloride, 2,6-dimethylbenzoyl chloride,2,4,6-trimethylbenzoyl chloride, 1-fluorene carbonyl chloride, p-anisoylchloride, 3,4,5-trimethoxybenzoyl chloride, p-toluoyl chloride,cyclohexane carbonyl chloride, picolinyl chloride or 2-thiophenecarbonyl chloride produces, respectively, 5'O-p-nitrobenzoylara-cytidine, 5'O-toluoyl ara-cytidine, 5'O-benzoyl ara-cytidine,5'O-2,6-dimethylbenzoyl ara-cytidine, 5'-O-2,4,6-trimethylbenzoylara-cytidine, 5'-O-1-fluorene carbonyl ara-cytidine, 5'-O-p-anisoylara-cytidine, 5'-O-3,4,5-trimethoxybenzoyl ara-cytidine, 5'O-p-toluoylara-cytidine, 5'O-cyclohexane carbonyl ara-cytidine, 5'-O-picolinylara-cytidine, and 5'-O-2-thiophene carbonyl ara-cytidine.

EXAMPLE 11 Preparation of 5'-O-adamantoyl ara-cytidine

5'-O-Trityl ara-cytidine (2.42 g., 5.0 millimoles) is dissolved in 50ml. of redistilled pyridine and cooled in a dri ice-acetone bath until aslurry formed. The slurry is treated with β,β,β-trichloroethoxycarbonyl(TCEC) chloride (3.2 g., 15 millimoles). The mixture is agitatedthoroughly and then allowed to stand at 0° for 20 hours. The reaction iswarmed to 25° and maintained at that temperature for 4 hours. Thepyridine is distilled at a temperature below 40° on a rotary evaporator.The residual gum is dissolved in 100 ml. of methylene chloride andwashed 4 times with 1 N hydrochloric acid. The methylene chloride layeris dried (Na₂ SO₄) and distilled. The residual gum is treated with 200ml. of 1% trifluoroacetic acid in chloroform for 2 hours at 25° toremove the trityl group. The chloroform solution is evaporated todryness and the gum dissolved in pyridine and treated withadamantane-1-carboxylic acid chloride (1-adamantane carbonyl chloride)(1.0 g., 5mM). The solution is warmed to 50° and maintained at thattemperature for 24 hours. The pyridine is distilled on a rotaryevaporator and the residue dissolved in 100 ml. of chloroform. Thechloroform solution is washed with 200 ml. of water, 200 ml. of 4%sodium bicarbonate and twice with 200 ml. of water. The chloroformsolution is dried (Na₂ SO₄) and distilled on a rotary evaporator. Theresidue is dissolved in 25 ml. of 90% acetic acid to which is added 2 g.of zinc dust. After standing 2 hours at room temperature the mixture isfiltered and the filtrate distilled. The residue is dissolved in aminimum amount of chloroform and absorbed onto a 300 g. column of silicagel. The desired product is eluted with chloroform-methanol-acetic acid(80:20:1). The material is crystallized from methanol, giving 250 mg. ofproduct.

EXAMPLE 12 Preparation of 5'-O-adamantoyl cytosine arabinosidehydrochloride

5'-O-adamantoyl cytosine arabinoside (42 g.) is suspended in 400 ml.methanol, and 12.5 ml. of concentrated hydrochloric acid is aded todissolve the material. Crystallization rapidly ensues and the mixture isdiluted to one liter with ether. The crystalline product is collected,washed with ether and dried, weight 32.9 g., m.p. 246° dec. The motherliquor is concentrated and a second crop obtained, weight 3.5 g., m.p.241° dec. (total yield = 36.4 g., 79%).

Substituting, as acylating agent, 1-norbornane carbonyl chloride,2-adamantane carbonyl chloride, 1-adamantaneacetyl chloride,α-chloro-3,5,7-trimethyl-1-adamantane acetyl chloride and 2-quinuclidinecarbonyl chloride produces, respectively, 1-norbornane carbonylara-cytidine, 5'-O-2-adamantane carbonyl ara-cytidine, 5'-O-1-adamantaneacetyl ara-cytidine, 5'-O-α-chloro-3,5,7-trimethyl-1-adamantaneara-cytidine, and 5'-O-2-quinuclidine carbonyl ara-cytidine.

EXAMPLE 13 Preparation of 5'-O-(p-toluenesulfonyl) ara-cytidine##STR112##

A 4.18 g. (10 millimoles) sample of N⁴ -trichloroethoxycarbonylara-cytidine is dissolved in 50 ml. of freshly distilled anhydrouspyridine. The solution is treated dropwise with 2.85 g. ofp-toluenesulfonyl chloride (15 millimoles) dissolved in 10 ml. ofpyridine. The reaction mixture is allowed to stir at room temperatureover the weekend, and then is poured into 60 ml. of water and taken todryness at 50° on a rotary evaporator. The crude gum is then dissolvedin 50 ml. of methanol and 5 g. of zinc dust added. The reaction mixtureis then heated to boiling for 15 minutes. TLC is checked and shows nostarting material left. The zinc is filtered and the preparation takento dryness. Th residue is then absorbed onto a 200 g. column of silicagel made up with cyclohexane, ethyl acetate, 95% EtOH (5:3:1). Thecolumn is eluted with 1 l. of this same solvent. This elutes only fastermoving material which is discarded. The column is then eluted with 15,100 ml. fractions of MEK*. acetone, H₂ O (72:20:8). Fractions 5-10contain what appears to be the desired product. These fractions move alittle slower than the starting material on TLC. and are combined andcrystallized from methanol. Yield 950 mg., m.p. 158°-168° (dec. at 195°). A sample is recrystallized from methanol for analysis, m.p.171°-174°.

Anal. Calcd. for C₁₆ H₁₉ O₇ N₃ S: C, 48.36; H, 4.82; N, 10.57; S, 8.04.

Found: C, 48.46; H, 5.25; N, 10.49; S, 8.13.

Ultraviolet Spectrum [λ _(max) ^(EtOH) (ε × 10⁻³)]: 224 (19.7); 269 sh(8.60); 273 (8.95).

Infrared Spectrum [γ_(cm).spsb.-1^(mull))]: 3480, 3330 sh, 3280 sh. 3240sh, 3210 sh, 1650, 1615, 1560 w, 1535, 1500, 1360, 1355, 1290, 1195,1175, 1070, 1040, 980, 835, 820, 800, 785, 665.

Infrared spectrum is proper for the sulfonate.

EXAMPLE 14 Preparation of 5'-O-cyclobutyl carbonyl ara-cytidine##STR113##

A 8.36 g. (20 millimoles) sample of N⁴ -trichloroethoxycarbonylara-cytidine is dissolved in 50 ml. of freshly distilled anhydrouspyridine. The solution is treated dropwise at room temperature withstirring with 4.0 g. (about 22 millimoles) of cyclobutanecarboxylic acidanhydride in 10 ml. of CH₂ Cl₂. The reaction mixture is allowed to stirat room temperature overnight and a TLC plate is run on the crudereaction in the morning. TLC still shows some starting material left, sothe preparation is heated to 50° in a water bath for 3 hours. TLC isunchanged so the reaction mixture is poured into 30 ml. of water andtaken to dryness at 50° on the rotry evaporator. The residue is thendissolved in CH₂ Cl₂ and washed once with saturated bicarbonate, twicewith water. At this point, there is a lot of precipitate in the CH₂ Cl₂layer. This is filtered and washed with a small amount of CH₂ Cl₂. Yield3.4 g. This material has one major spot with a trace of the slowermoving starting material. The CH₂ Cl₂ solution (the mother liquors)contain 3 faster moving spots plus a trace of the crystalline solid plusthe starting material. The 3.4 g. of crystalline solid is dissolved in100 ml. of methanol and heated to boiling with 3.5 g. of zinc dust for10 minutes on the steam bath. TLC shows no starting material left atthis point. The zinc is filtered off and the methanol solution taken todryness at 50° on the rotary evaporator. The clear residue is thenabsorbed onto a 200 g. column of silica gel made up with MEK, acetoneand H₂ O (72:20:8) and the column eluted with 15, 50 ml. fractions ofthe same solvent. Based on TLC results, fractions 9-13 are combined andrecrystallized from acetone. Yield 1.045 g. Recrystallized from acetonefor analysis, a sample has a m.p. 200.0°-200.5°. TLC is the same as thefirst crop material.

Anal. Calcd. for C₁₄ H₁₇ O₆ N₃ : C, 51.68; H, 5.89; N, 12.92.

Found: C, 51.29; H, 6.13; N, 13.25.

Ultraviolet Spectrum [λ _(max) ^(EtOh) (ε × 15⁻³)]: 230 sh (7.90); 273(9.00).

Infrared Spectrum [γ_(cm).spsb.-1^(mull) ]: 3440, 3330, 3260, 3210,1700, 1655, 1635, 1600, 1525, 1295, 1255, 1185, 1135, 1105, 1050, 810.

Ultraviolet spectrum, infrared spectrum and NMR are proper for theproposed structure.

EXAMPLE 15 Preparation of 5'-O-(p-anisoyl) ara-cytidine ##STR114##

A 8.36 g. (20 millimoles) sample of N⁴ -trichloroethoxycarbonylara-cytidine is dissolved in 50 ml. of freshly distilled anhydrouspyridine. The solution is treated dropwise with stirring at roomtemperature with 3.75 g. (22 millimoles) of anisoyl chloride in 10 ml.of CH₂ Cl₂. The reaction mixture is allowed to stir at room temperatureovernight and a TLC plate is run on the crude mixture in the morning.TLC still shows some starting material left. The preparation is heatedto 50° in a water bath for 3 hours. TLC is unchanged so the reactionmixture is poured into 30 ml. of water and taken to dryness at 50° on arotary evaporator. The residue is dissolved in CH₂ Cl₂ and washed oncewith 100 ml. of saturated bicarbonate, once with H₂ O and dried oversodium sulfate. The CH₂ Cl₂ solution is then absorbed onto a 200 g.column of silica gel and eluted with 20, 50 ml. fractions ofcyclohexane, ethyl acetate, 95% EtOH (5:3:1). Based on TLC results,fractions 10- 18 are combined in methanol (100 ml.) and treated with 4g. of zinc dust for 15 minutes at reflux on the steam bath. TLC at thispoint shows no starting material left so the solution is filtered freeof zinc and the preparation taken to dryness on the rotary evaporator.The residue is then absorbed onto a 200 g. column of silica gel made upwith MEK, acetone. H₂ O and eluted with 20, 50 ml. fractions of the samesolvent. Based on TLC results, fractions 10- 16 are combined andrecrystallized from methanol. Yield 795 mg., m.p. 225°-227° (dec.).Recrystallized from methanol a sample for analysis has m.p. 225°-227°(dec.).

Anal. Calcd. for C₁₇ H₁₉ O₇ N₃ : C, 54.11; H, 5.08; N, 11.14.

Found: C, 53.95; H, 4.81; N, 11.09.

Ultraviolet Spectrum [λ_(max) ^(EtOH) (ε × 10⁻³)]: 258 (14.50); 271 slsh (19.20); 278 sl sh (13.00); 283 sl sh (4.90).

The shift in the main absorption is due to the ##STR115## group as the278 and 283 sl sh's. Ultraviolet spectrum supports the proposedstructure.

Infrared Spectrum [γ_(cm).spsb.-1^(mull) ]: 3420, 3310, 1720, 1665,1630, 1600, 1530, 1510, 1490, 1275, 1250, 1170, 1100, 1035, 850, 825,790, and 770.

NMR and infrared spectrum are proper for the proposed structure.

EXAMPLE 16 Preparation of 5'-O-cyclohexyl carbonyl ara-cytidine##STR116##

A 8.36 g. (20 millimoles) sample of N⁴ -trichloroethoxycarbonylara-cytidine is dissolved in 50 ml. of freshly distilled anhydrouspyridine. The solution is treated dropwise with stirring and at roomtemperature with 3.22 g. (about 22 millimoles) of cyclohexanecarboxylicchloride in 10 ml. of CH₂ Cl₂. The chloride is made by refluxingcyclohexanecarboxylic acid in thionyl chloride, removing the thionylchloride on the rotary evaporator and distilling the chloride, boilingpoint 180°-181°. The reaction mixture is allowed to stir at roomtemperature overnight. A TLC is run on the crude mixture in the morning.The TLC still shows some starting material left so the preparation isheated to 50° in a water bath for 3 hours. The reaction mixture ispoured into 30 ml. of water and taken to dryness at 50° on the rotaryevaporator. The residue is then absorbed onto a 200 g. column of silicagel. and eluted with 25, 50 ml. fractions of cyclohexane, ethylacetate,95% EtOH (5:3:1). The column is made up with the same solvent. TLC's arerun on fractions 5- 14 and on fraction 23. Based on TLC results,fractions 6- 11 are combined. 3.387 g. in 100 ml. of methanol is treatedwith 4 g. of zinc dust at reflux for 15 minutes. TLC shows no startingmaterial left at this point. The zinc is filtered off and the filtratetaken to dryness at 50° on the rotary evaporator. The residue is thenabsorbed onto a 200 g. column of silica gel made up with MEK, acetone,H₂ O (72:20:8) and eluted with 20, 50 ml. fractions of the same solvent.Based on TLC results, fractions 10- 14 are combined and recrystallizedfrom methanol-acetone. Yield 1.384 g., m.p. sinters at 206° dec. at 229°(one spot by TLC). Recystallized 100 mg. from the same solvent, a samplefor analysis sinters about 210° and dec. at 231°.

Anal. Calcd. for C₁₆ H₂₃ O₆ N₃.1/2 H₂ O: C, 53.03; H, 6.68; N, 11.60

Found: C, 52.85; H, 6.66; N, 11.95

Ultraviolet Spectrum [λ_(max) ^(EtOH) (ε × 10⁻³)]: 315 sl sh (10.20);230 sh (7.65); 273 (8.75).

Infrared Spectrum [γ_(cm).spsb.-1^(mull) ]: 3420, 3340, 3210, 1735,1715, 1655, 1640, 1625, 1530, 1490, 1285, 1245, 1200, 1180, 1110, 1095,1055, 815, and 780.

Ultraviolet spectrum supports the proposed structure.

NMR and infrared spectrum are proper for the proposed structure.

EXAMPLE 17 Preparation of 5'-O-β-chloropivaloyl ara-cytidine ##STR117##

A 8.36 g. (20 millimoles) sample of N⁴ -trichloroethoxycarbonylara-cytidine is dissolved in 50 ml. of freshly distilled anhydrouspyridine. The solution is treated dropwise with stirring at roomtemperature with 3.4 g. (about 22 millimoles) of β-chloropivalic acidchloride. The chloride is made by refluxing β-chloropivalic acid(Aldrich) in an excess of thionyl chloride, distilling off the thionylchloride, then the acid chloride, b.p. 158°-160°. After 18 hours at roomtemperature there is still starting material left by TLC. Another 3.4 g.of the acid chloride is added in 10 ml. of CH₂ Cl₂. After 4 hours atroom temperature the TLC is still mostly unchanged. The reaction mixtureis warmed on the steam bath for 5- 10 minutes. TLC at this point showsonly a trace of the starting material. The preparation is poured into 60ml. of water and taken to dryness on the rotary evaporator at 50°. Theresidue is then absorbed into a 200 g. column of silica gel made up withcyclohexane, ethyl acetate, 95% EtOH (5:3:1) and eluted with 20, 50 ml.fractions of the same solvent. Fractions 6-20 are slurried in a smallamount of methanol and filtered and washed with 10-15 ml. of coldmethanol. This material has one major spot by TLC with a trace of fastermoving material and a trace of the starting material. Yield is 6.85 g.This material is dissolved in 100 ml. of methanol and heated to refluxwith 7 g. of zinc dust for 15 minutes. TLC shows no starting materialleft so the zinc was filtered off, washed with methanol and the filtratetaken to dryness at 50° on the rotary evaporator. The residue isabsorbed onto a 200 g. column of silica gel and eluted with 25, 50 ml.fractions of MEK, acetone, H₂ O (72:20:8). TLC's are run on crystallinefractions 11, 15 and 21. Based on TLC results, fractions 11- 21 arecombined and recrystallized from methanol. The compound will crystallizefrom H₂ O also. Yield 2.50 g., m.p. 238°-40° dec. A samplerecrystallized for analysis from the same solvent has m.p. 238°-40° dec.One spot by TLC.

Anal. Calcd. for C₁₄ H₂₀ O₆ N₃ Cl: C, 46.48; H, 5.57; N, 11.61; Cl, 9.80

Found: C, 46.42; H, 5.68; N, 11.46; Cl, 10.16.

Ultraviolet Spectrum [λ_(max) ^(EtOH) (ε× 10⁻³)]: 216 sl sh (10.20); 229sh (7.90); 273 (9.05).

Infrared Spectrum [γ_(cm).spsb.-1^(mull) ]: 3410, 3440, 3340, 3260,3220, 1710, 1655, 1635, 1600, 1565, 1525, 1485, 1300, 1255, 1190, 1125,1100, 1055, and 810.

EXAMPLE 18 Preparation of ara-cytidine 5'-methyl carbonate ##STR118##

A 4.18 g. (10 millimoles) sample of N⁴ -trichloroethoxycarbonylara-cytidine is dissolved in 25 ml. of freshly distilled anhydrouspyridine. The solution is treated dropwise at room temperature with 1.0g. of methyl chloroformate (about 22 millimoles) dissolved in 10 ml. ofCH₂ Cl₂. The solution is allowed to stir at room temperature overnightand the TLC is checked in the morning. TLC showed some starting materialleft. The preparation is taken to dryness at 50° on the rotaryevaporator and the residue absorbed onto a 150 g. column of silica gelmade up with cyclohexane, ethyl acetate, 95% EtOH (5:3:1). The column iseluted with 20, 50 ml. fractions of the same solvent. TLC's of fractions9- 17 shows fractions 10- 13 to contain the desired ##STR119##derivative of N⁴ -trichloroethoxycarbonyl ara-cytidine. These fractionsof 2.465 g. are combined in 50 ml. of methanol and treated at reflux for15 minutes on the steam bath with 3 g. of zinc dust. TLC shows nostarting material left. The zinc is then filtered and the preparationtaken to dryness on the rotary evaporator. The residue is then absorbedonto a 150 g. column of silica gel made up with MEK, acetone, methanol(5:2:3) and eluted with 25, 50 ml. fractions of the same solvent. TLC'sare run on fractions 17- 22 and based on the TLC results, fractions19-22 are combined and recrystallized from methanol. Yield is 390 mg.,m.p. 188.5°-90° dec. (foamed up the tube).

Anal. Calcd. for C₁₁ H₁₅ O₇ N₃ : C, 43.85; H, 5.02; N, 13.95. Found: C,44.16; H, 5.26; N, 13.64.

Ultraviolet Spectrum [λ_(max) ^(EtOH) (ε × 10⁻³)]: 215 sl sh (10.35);230 (8.00); 273 (9.15).

Infrared Spectrum [λ_(cm).spsb.-1^(mull) ]: 3460, 3340, 3250, 3230,3180, 1765, 1640, 1625, 1560, 1530, 1500, 1315, 1280, 1090, 1070, 1035,990 and 780.

Ultraviolet spectrum, infrared spectrum and NMR are all proper for theproposed structure.

EXAMPLE 19 Preparation of 5'-O-(p-nitrobenzoyl) ara-cytidine ##STR120##

A 8.36 g. (20 millimoles) sample of N⁴ -trichloroethoxycarbonylara-cytidine is dissolved in 25 ml. of freshly distilled anhydrouspyridine. The solution is treated dropwise with 4.08 g. (about 22millimoles) of p-nitrobenzoyl chloride dissolved in 25 ml. of thefreshly distilled anhydrous pyridine. The solution is allowed to stirovernight at room temperature. TLC in the morning shows only a smallamount of starting material left. The reaction mixture is poured into 25ml. of water and taken to dryness at 50° on the rotary evaporator. Theresidue is absorbed onto a 200 g. column of silica gel made up withcyclohexane, ethyl acetate, 95% ethanol and eluted with 20, 50 ml.fractions of the same solvent. Fractions 7-16 are combined after TLC'sare run on the fractions, slurried in methanol, the crystalline solidfiltered and washed with a small amount of methanol. Yield 4.0 g. Thismaterial is then dissolved in 100 ml. of methanol and treated with 4.0g. of zinc dust at reflux for 15 minutes on the steam bath. No startingmaterial is left at this point. The zinc is filtered off and thepreparation taken to dryness. The solid is extracted with methanol andthe extracts added to a 200 g. column of silica gel and eluted with 20,50 ml. fractions of MEK, acetone, H₂ O (72:20:8). Fraction 14 contains afew mgs. of crystals which are recrystallized from acetone-H₂ O, m.p.244°-245° dec. This material moves on TLC at about the same rate as the5'-O-benzoyl CA, 35'-O-benzoyl and the 2'-O-benzoyl CA.

EXAMPLE 20 Preparation of 5'-O-2,4,6-triisopropylbenzenesulfonylara-cytidine ##STR121##

A 4.18 g. (10 millimoles) sample of N⁴ -trichloroethoxycarbonylara-cytidine is dissolved in 50 ml. of freshly distilled anhydrouspyridine. The solution is treated dropwise with 4.54 g. (15 millimoles)of 2,4,6-triisopropylbenzenesulfonyl chloride dissolved in 10 ml. ofpyridine. The reaction mixture is allowed to stir at room temperatureover the weekend then poured into 60 ml. of water and taken to drynessat 50°. This crude gum is then dissolved in 50 ml. of methanol, 5 g. ofzinc dust added and the reaction mixture heated to boiling for one-halfhour on the steam bath. TLC shows no starting material left. Thepreparation is filtered free of zinc and taken to dryness on the rotaryevaporator. The crude gum is then absorbed onto a 200 g. column ofsilica gel and eluted with 20, 100 ml. fractions of MEK, acetone and H₂O. Fractions 7-20 all show one spot by TLC moving a little slower thanthe starting material and appearing to be the desired product. A 1 l.strip fraction of methanol is taken and also contains some material thatwas one spot moving with the fractions 7-10. Fractions 7-20 and the 1 l.methanol strip are combined, taken to dryness and crystallized once frommethanol-water, then again from methanol. Yield 1.175 g., m.p.188.5°-89.5° sl. dec. Another m.p. on the same sample does not meltuntil 228° and it dec. Recrystallized, from methanol a sample foranalysis, m.p. 228° dec.

Anal. Calcd. for C₂₄ H₃₅ O₇ N₃ S: C, 56.56; H, 6.92; N, 8.25; S, 6.29.Found: C, 56.58; H, 6.94; N, 8.23; S, 6.08.

Ultraviolet Spectrum [λ _(max) ^(EtOH) (ε × 10⁻³)]: 228 (17.85); 274(10.60); 283 sl sh (8.60).

Infrared Spectrum [γ_(cm).spsb.-1^(mull) ]: 3350, 3280, 3220, 3160 sh.1665, 1640, 1615, 1575 sh. 1530, 1495, 1350, 1290, 1180, 1100, 1090,1010, 980, 960 and 790.

NMR and the infrared spectrum are proper for the sulfonate.

EXAMPLE 21 Preparation of 5'-O-isobutyryl ara-cytidine ##STR122##

A 8.36 g. (20 millimoles) sample of N⁴ -trichloroethoxycarbonylara-cytidine is dissolved in 10 ml. of freshly distilled anhydrouspyridine. The solution is treated with 3.5 g. (about 22 millimoles) ofisobutyric anhydride dropwise at room temperature with stirring. Thereaction mixture is allowed to stir at room temperature overnight. A TLCis run on the crude reaction in the morning. 25 ml. of water is added tothe preparation and the preparation is taken to dryness at 50°. Theglassy residue is then absorbed onto a 200 g. column of silica gel andeluted with 10, 100 ml. fractions of cyclohexane, ethyl acetate, 95%EtOH (5:3:1). TLC's are run on the first of the fractions. Fractions 5and 6 are combined on the basis of the TLC results and recrystallizedfrom methanol. Yield 2.0 g., m.p. 255° dec. One spot by TLC. This 2.0 g.of material is then dissolved in 50 ml. of methanol and treated with 2.0g. of zinc dust at reflux for 10 minutes on the steam bath. TLC shows nostarting material left. The zinc is filtered off and the methanolremoved at 50° on the rotary evaporator. The clear glassy residue isthen absorbed onto a 200 g. column of silica gel made up withcyclohexane, ethyl acetate, 95% EtOH (5:3:1). The column is eluted with1 l. of the same solvent. Only a small amount of oil is eluted. Thecolumn is then eluted with 12, 100 ml. fractions of methyl ethyl ketone,acetone, H₂ O (72:20:8). TLC's are run on fractions 5 through 9. On thebasis of the results fractions 7, 8 and 9 are combined andrecrystallized from water. Yield, 990 mg., m.p. 179°-184°.Recrystallized from water once for analysis, a sample has m.p.206°-208°. (Heating rate about 3° per minute. Melting point varies.) Ifput in bath at 180°, sample melts immediately. If heating rate was15°-20° per minute, m.p. 212-214°.

Anal. Calcd. for C₁₃ H₁₉ O₆ N₃ · 1/2 H₂ O: C, 48.44; H, 6.25; N, 13.04Found: C, 48.62; H, 5.98; N, 13.33

Ultraviolet Spectrum [λ _(max) ^(EtOH) (ε × 10⁻³)]: 233 sl sh (7.60);273 (8.70).

Infrared Spectrum [γ _(cm).spsb.-1^(mull) ]: 3400, 3340, 328 sh, 3210,3120 sh, 1740, 1715, 1655, 1640, 1625, 1535, 1490, 1285, 1205, 1165,1110, 1095, 1050, 815, and 780.

EXAMPLE 22 Preparation of 5'-O- 3,4,5-trimethoxybenzoyl ara-cytidine##STR123##

A 8.36 gram (20 millimole) sample of N⁴ -trichloroethoxycarbonylara-cytidine is dissolved in 100 ml. of freshly distilled anhydrouspyridine. The solution is treated with stirring and at room temperaturewith 4.85 g. (about 22 millimole) of 3,4,5-trimethoxybenzoyl chloride.Reaction is allowed to stir overnight at room temperature. A TLC was runin the morning, in the system silica gel, cyclohexane, ethyl acetate,95% EtOH. The solution still shows starting material left. The reactionmixture is heated to 50° in an oil bath overnight. TLC plate shows nostarting material in the crude mixture. Compound streaks and is hard torecognize. A white solid that precipitates out of the solution isspotted also. This material does not move from the origin. The reactionmixture is poured into 60 ml. of water and taken to dryness on therotary evaporator. The gum is absorbed onto a 200 g. column of silicagel and eluted with 15, 100 ml. fractions of cyclohexane, ethyl acetate,95% EtOH. Column is made up with this solvent also. On the basis of TLCresults, fractions 4-9 are combined in methylene chloride, washed oncewith saturated bicarbonate once with water, dried through sodium sulfateand taken to dryness. This removes all the slower moving material whichis the trimethoxy benzoyl acid by TLC. The residue is dissolved in 100ml. methanol and 3 g. zinc dust were added. This mixture was heated atthe reflux temperature for 10-15 mins. and then cooled. The cooledsolution was filtered to remove zinc dust, and the methanol was removedby evaporation at 50° C. The residue thus obtained (8.17 g.) wasdissolved in methylene chloride and absorbed onto a 200 g. column ofsilica gel made up with MEK, acetone, H₂ O (72:20:8) and eluted with 12,100 ml. fractions of the same solvent. Fractions 6, 7, 8 and 9 arespotted on a TLC plate and run in the same solvent. Based on the TLCresults fractions 7, 8 and 9 are combined and recrystallized frommethanol. Yield 2.410 g., m.p. 143°-145°. Recrystallized from methanol,a sample for analysis shows, m.p. 137°-139°.

Anal. Calcd. for C₁₉ H₂₃ O₉ N₃ ·I H₂ O: C, 50.11; H, 5.53; N, 9.23Found: C, 50.50; H, 5.41; N, 9.15.

Ultraviolet Spectrum [λ_(max) ^(EtOH) (ε × 10⁻³)]: 214 (40.30); 269(17.75); 305 sl sh (2.55).

Infrared Spectrum [γ_(cm).spsb.-1^(mull) ]: 3420, 3320, 3260, 3220,1715, 1645, 1600, 1520, 1500, 1340, 1280, 1225, 1125, 1095, 1075, 1065,1030, 995, 860, and 805.

Both ultraviolet spectrum and infrared spectrum are proper for theproposed structure.

EXAMPLE 23 Preparation of 5'-O- 2,6-dimethylbenzoyl ara-cytidine##STR124##

A 8.36 g. (20 millimole) sample of N⁴ -trichloroethoxycarbonylara-cytidine is dissolved in 100 ml. of freshly distilled anhydrouspyridine. The solution is treated at room temperature with 3.70 g.(about 22 millimole) of 2,6 -dimethylbenzoic chloride. The reactionmixture is stirred overnight. The chloride is dissolved in 10 ml. of CH₂Cl₂ and added dropwise. TLC in the morning shows some starting materialleft. Another 3.70 g. in 10 ml. of CH₂ Cl₂ is added dropwise and thepreparation allowed to go overnight at room temperature. In the morningTLC shows almost no starting material left. 50 ml. of water are addedand the preparation taken to dryness at 50° on a rotary evaporator. Theresidue is dissolved in 200 ml. of CH₂ Cl₂ and extracted twice with 100ml. each of saturated bicarbonate. The CH₂ Cl₂ solution is washed oncewith 200 ml. of H₂ O and dried through sodium sulfate, then taken todryness. The gum is then absorbed onto a 200 g. column of silica gelmade up with cyclohexane, ethyl acetate, 95% EtOH. The column is elutedwith 20, 100 ml. fractions of the same solvent. TLC's are run onfractions 7-15. Based on the TLC results, fractions 7-12 are combinedand recrystallized from methanol. Yield 3.0 g. This material has onespot by TLC and moves the same on the plate as 2,4,6-trimethylbenzoyl N⁴-trichloroethoxycarbonyl ara-cytidine. This 3 g. of material isdissolved in 100 ml. of methanol, 3 g. of zinc dust added and thepreparation heated to reflux for 15 minutes on the steam bath. At thistime TLC shows no starting material left. The zinc is filtered off andthe methanol removed in the evaporator. The clear glassy residue is thenabsorbed onto a 200 g. column of silica gel made up with MEK, acetone,H₂ O (72:20:8) and eluted with 10, 100 ml. fractions of the samesolvent. TLC's are run on fractions 3, 4, 5 and 7. Fractions 4-9 arecombined and recrystallized from methanol. The yield is 1.24 g. m.p.238°-240° dec. A sample is recrystallized once from methanol foranalysis, m.p. 238°-240° dec.

Anal. Calcd. for C₁₈ H₂₁ O₆ N₃ · 1/2 H₂ O: C, 56.24; H, 5.77; N, 10.93.Found: C, 56.31; H, 6.03; N, 11.17

Ultraviolet Spectrum [λ _(max) ^(EtOH) (ε × 10⁻³)]: 233 sl sh (10.25);273 (9.55).

Infrared Spectrum [ε_(cm).spsb.-1^(mull) ]: 3500 sh. 3400, 3340, 3280 w,3220, 1740 sh, 1715, 1655, 1635, 1615, 1530, 1485, 1785, 1270, 1245,1110; 1095, 1070, 1050, 815 and 710.

EXAMPLE 24 Preparation of 5'-O-palmityl ara-cytidine

Ara-cytidine hydrochloride (2.80 g., 0.01 mole) is dissolved in 25 ml.dimethylformamide and 3.05 g. (0.011 mole) of palmityl chloride isadded. The solution is allowed to stand at room temperature for 7 hours.The solvent is evaporated in vacuo (oil pump) and the resultant oil isstirred with 70 ml. of 0.3N sodium bicarbonate. The resultant solid iscollected on a filter, washed several times with water, pressed dry, andthen washed three times with 25 ml. ethyl acetate and air dried. Yield,2.52 g. (52%), m.p. 135°-145°. Thin layer chromatography showed a singleultraviolet-absorbing spot in several solvent systems. A sample isrecrystallized once from methanol (82% recovery) for analysis, m.p.145°-148°.

Anal. Calcd. for C₂₅ H₄₃ N₃ O₆ : C, 62.34; H, 9.00; N, 8.72. Found: C,62.65; H, 9.29; N, 8.75

Infrared and ultraviolet absorption curves are identical to that of anauthentic sample, and the material is chromatographically identical tothe authentic sample in several solvent systems.

EXAMPLE 25 Preparation of 5'-pivaloyl ara-cytidine

Ara-cytidine hydrochloride (3.5 g., 0.01 mole on the basis of 20.5%solvent of crystallization), is suspended in 25 ml. of dimethylacetamideand 1.3 g. (10% excess) of pivaloyl chloride is added. The mixture isstirred at room temperature. As the material reacts it slowly dissolves.After stirring overnight, the mixture is clear. The solution isconcentrated to a low-volume in vacuo (oil pump) and the residual oil isstirred with 100 ml. ethyl acetate-ether (1:1). This treatment isrepeated twice more, decanting and centrifuging. The semi-solid is thentriturated with 20 ml. of N NaHCO₃, filtered, and washed several timeson the filter with water. The white crystalline solid is dried in an airstream. Yield 2.24 g. (66%), m.p. 252°-258° dec. TLC (EtOAC-DMF-H₂ O,75:15:5) shows that the material consist of a single spot*, Rf = 0.38.About 1 g. of this material is recrystallized from 15 ml. methanol.Recovery 0.4 g., m.p. 261°-262° dec. The remainder of the material (1.24g.) is stirred with hot butanol. It changes crystalline form and becomessparingly soluble in the butanol. A total of 25 ml. of hot butanol isused, but much remains insoluble. Recovery 1.04 g., m.p. 259°-260° dec.The mother liquors are combined, evaporated to dryness, and the residueis recrystallized from methanol. Recovery 0.36 g., m.p. 254°-256° dec.

EXAMPLE 26 Preparation of 5'-octanoyl ara-cytidine

Ara-cytidine hydrochloride (5.6 g., 0.02 mole) is dissolved in 50 ml.dimethylformamide and 3.6 g. (0.022 mole) of octanoyl chloride is added.The clear solution is allowed to stand over the weekend.

TLC shows that a good yield of the product (Rf = 0.38 run with anauthentic sample as standard) is obtained, with a trace of a componentof Rf = 0.95, small amounts of other products of Rf's = 0.70, 0.52,0.24, and material of low Rf trailing to the origin. The solvent isevaporated with vacuum and the oil is stirred with about 100 ml. etherthree times. The semi-solid is then thoroughly stirred with 40 ml. NNaHCO₃, the resultant solid is collected and washed with H₂ O untilneutral. The solid is air-dried. Weight 4.89 g. TLC (as above) showsthat the product at this stage has a small amount of materials of Rf's =0.70 and 0.52 and a trace of material trailing behind the product. Theproduct is crystallized from 60 ml. hot ethyl acetate as needles.Recovery 4.07 g. (55%), m.p. 158°-161°.

EXAMPLE 27 Preparation of 5'-cyclohexylcarbonyl ara-cytidine

Ara-cytidine hydrochloride (20% by weight of solvent; 17.5 g., 0.05mole) is dissolved in 125 ml. dimethylformamide and 8.06 g. (10% excess)of cyclohexanecarboxylic acid chloride is added. The clear solution isallowed to stand at room temperature overnight.

The solvent is evaporated in vacuo and the oil is stirred several timeswith ether. The oil is then thoroughly triturated with 100 ml. N sodiumbicarbonate. The solid is filtered, washed with water and air dried. Thematerial is crystallized from 100 ml. ethyl acetate. The materialdissolves readily in warm ethyl acetate and then crystallizes out in aform that will not redissolve in this solvent. The crystalline materialis collected, washed with ethyl acetate, ether and dried. Weight 5.58g., m.p. 232° dec. The mother liquor is evaporated to dryness and thecrystalline residue is triturated with hot ethyl acetate, cooled andcollected as above. Weight 3.86 g., m.p. 227°-229° dec. Total yield 9.44g. (53%). The Rf is identical to that of an authentic sample.

EXAMPLE 28 Preparation of 5'-acetyl-ara-cytidine

Ara-cytidine hydrochloride dimethylformamide solvate (17.5 g., 0.05mole) is dissolved in 125 ml. dimethylformamide and 4.32 g. (10% excess)of acetyl chloride is added. The clear solution is allowed to standovernight at room temperature.

The solvent is evaporated in vacuo, and the resulent oil is stirredseveral times with ether. The residual oil is dissolved in water, the pHis adjusted to 1.5, and the solution is extracted three times with equalvolumes of ethyl acetate. The pH of the aqueous solution is adjusted to7, and the solvent is evaporated in vacuo. The residual oil is dissolvedin ethanol and sodium chloride is removed by filtration. The solvent isevaporated in vacuo to leave an oil weighing 16.5 g.

About 13 g. of this product is purified by chromatography over silicagel (Merck-Darmstadt, 0.05-0.2 mm) using the solvent systemmethylethylketone-acetone-water (72:20:8). About 800 g. of adsorbent fora column 56 mm in diameter is used. The material is dissolved in a smallvolume of water for adsorption on the column, and then elution with thesolvent is begun. The volume of each fraction is 100 ml., and theelution of the material is followed by TLC. The 5'-acetyl ara-cytidineis eluted in fractions 33-51, which is combined and evaporated in vacuoto leave a crystalline residue weighing 7.0 g. The product isrecrystallized from 60 ml. 1-butanol, recovery 4.05 g., m.p. 184°-185°.TLC in several solvent systems shows that the material ischromatographically identical to an authentic sample of 5'-acetylara-cytidine. A small amount of additional product is recovered from themother liquor above to give a total yield of purified product of 38%.

EXAMPLE 29 Preparation of 5'-adamantoyl ara-cytidine

Ara-cytidine hydrochloride (63 g., 0.225 mole) is suspended in 1100 ml.of dimethylacetamide. About 51 g. (10% excess) of 1-adamantanecarboxylicacid chloride is added and the mixture is stirred overnight at roomtemperature. The mixture is filtered to remove about 4.8 g. of solid.TLC of the filtrate shows a considerable amount of unreacted cytosinearabinoside. An additional 32 g. (0.16 mole) of 1-adamantanecarboxylicacid chloride is added and the reaction is allowed to proceed for anadditional 24 hours. The solution is concentrated in vacuo to a lowvolume and the oil is triturated three times with 500 ml. of ethylacetate-ether (1:1). The oil is thoroughly triturated with 650 m. NNaHCO₃, the resultant crystalline solid is collected by filtration andwashed several times with water. The filter cake is pressed dry and thesolid is washed twice with ethyl acetate and then with ether, and dried.Yield, 63 g. (69%), m.p 282° dec. Recrystallization from 400 ml.dimethylacetamide-1600 ml. ethyl acetate gives 61.1 g., m.p. 291° dec.TLC in several solvent systems, and comparative melting pointdeterminations show that the product is identical to an authentic sampleof 5'-adamantoyl aracytidine.

EXAMPLE 30 Preparation of 5'-O-L-trans-3-[n-propyl]-hygric acid ester ofara-cytidine

L-trans-3-[n-propyl]-hygric acid hydrochloride is heated to reflux inexcess thionyl chloride until the acid is completely dissolved. Theexcess thionyl chloride is then removed by distillation under reducedpressure. The residue is taken to dryness three times with 5 volumes ofdry benzene. The residue is then dissolved in a minimum amount of drydimethylacetamide and added to a solution of ara-cytidine hydrochloridein the same solvent and stirred at room temperature overnight. The5'-ester is then isolated as described in Example 22.

EXAMPLE 31 Preparation of 5'-lauroyl-ara-cytidine

Ara-cytidine hydrochloride (5.0 g., 0.018 mole) is dissolved in 45 ml.dimethylformamide and 4.33 g. (0.02 mole) of lauroyl chloride is addeddropwise. The reaction mixture is stirred overnight at room temperature.The solvent is evaporated at reduced pressure and the resulting gumtriturated with 1N sodium bicarbonate. The resulting precipitate isfiltered and dissolved in a minimum volume of acetone and the solutionfiltered. The solution is allowed to cool to room temperature and theproduct crystallizes. After all apparent crystallization has occurred,it is stored in the freezer overnight. Filtration provides 4.6 g. (60%)of a white solid, m.p. 153°-155° C. TLC (MEK*:acetone:H₂ O, 60:20:15)shows one zone, Rf=0.57.

Analysis: Calc'd. for C₂₁ H₃₅ N₃ O₆ ·1/2H₂ O: C, 58.04; H, 8.35; N,9.67.

Found: C, 58.10; H, 8.59; N, 9.50.

Infrared Spectrum [γ_(cm).spsb.-1^(mull) ]: 3400, 3340, 3230, 1735,1635, 1600, 1535, 1485, 1280, 1165, 1110 and 1040.

EXAMPLE 32 Preparation of 5'-O-lauroyl-ara-cytidine hydrochloride

Following the procedure of Example 7, 5'-O-lauroyl-ara-cytidinehydrochloride is prepared by substituting 5'-O-lauroyl-ara-cytidine for5'-palmityl cytosine arabinoside.

EXAMPLE 33 Tablets for Oral Administration

1000 Scored tablets for oral use, each containing 500 mg. of5'-O-palmityl ara-cytidine, are prepared from the following types andamounts of ingredients:

    ______________________________________                                        5'-0-palmityl ara-cytidine                                                                         500       gm.                                            Starch, U.S.P.        35       gm.                                            Talc, U.S.P.          25       gm.                                            Calcium stearate     3.5       gm.                                            ______________________________________                                    

The powdered 5'-O-palmityl ara-cytidine is granulated with a 4% w./v.aqueous solution of methylcellulose U.S.P. To the dried granules isadded a mixture of the remainder of the ingredients and the finalmixture is compressed into tablets of proper weight.

Satisfactory clinical response is obtained in adults with acute leukemiawith 1 tablet 3 times a day.

Using the procedure above, tablets are similarly prepared containing5'-O-palmityl ara-cytidine in 3 mg. and 1000 mg. amounts by substituting3 gm. and 1000 gm. of 5'-O-palmityl ara-cytidine for the 500 gm. usedabove.

EXAMPLE 34 Injectable Dispersion

A sterile aqueous dispersion suitable for intramuscular use, andcontaining 250 mg. of 5'-O-palmityl ara-cytidine hydrochloride in eachml., is prepared from the following ingredients:

    ______________________________________                                        5'-0-palmityl ara-cytidine                                                    hydrochloride        250       gm.                                            Water for injection, q.s.                                                                          1,000     gm.                                            ______________________________________                                    

A daily dose of 1 ml. provides a satisfactory clinical response.

EXAMPLE 35 Injectable Preparation

A sterile aqueous preparation suitable for intramuscular injection andcontaining 10 mg. of 5'-O-palmityl ara-cytidine in each 2 ml. isprepared from the following ingredients:

    ______________________________________                                        5'-0-palmityl ara-cytidine                                                                          5         gm.                                           Polyethylene glycol, 4000 U.S.P.                                                                    30        gm.                                           Sodium chloride, U.S.P.                                                                             9         gm.                                           Preservative, q.s.                                                            Water for injection, q.s.                                                                           1,000     ml.                                           ______________________________________                                    

EXAMPLE 36 Injectable Preparation

A sterile preparation suitable for intramuscular injection andcontaining in each milliliter 100 mg. of 5'-O-palmityl ara-cytidine isprepared from the following types and amounts of materials:

    ______________________________________                                        5'-0-palmityl ara-cytidine                                                                          100       gm.                                           Aluminum monostearate-peanut                                                  oil gel, q.s. to      1,000     gm.                                           ______________________________________                                    

A mixture of 2 parts aluminum monostearate and 98 parts of peanut oil isslowly heated with stirring to a temperature of 100° C. The temperatureis maintained at this level for 1 hour when gelling is complete and isthen raised to 150° C. and maintained at this temperature for 1 hour.The gel is then cooled and 100 grams of sterile, powdered 5'-O-palmitylara-cytidine is incorporated aseptically with stirring and the totalvolume made up to 1000 ml. with additional gel and further stirring.

EXAMPLE 37 Sterile Powder for Reconstitution

Sterile vials each containing 50 mg. of 5'-O-palmityl ara-cytidinehydrochloride are prepared by first sterilizing 50 gm. of the5'-O-palmityl ara-cytidine by treatment with ethylene oxide andthereafter filling 50 mg. into each of 1000 sterile vials. At the timeof use, the contents of a vial are reconstituted with q.s. water forinjection to provide a sterile preparation for injection administration.

EXAMPLE 38 Sterile Preparation

24,000 Ml. of sterile preparation are prepared as follows:

    ______________________________________                                        Each mil.:             Total                                                  57.5 mg. 5'-0-palmityl ara-                                                   cytidine hydrochloride 1380 gm.                                               5 mg. sodium citrate    120 gm.                                               9.45 mg. benzyl alcohol                                                                               227 gm.                                               2.3 mg. sodium bisulfite                                                                             55.2 gm.                                               Sodium hydroxide (50% aqueous                                                 solution), q.s.                                                               Water for injection, q.s. ad                                                                         24,000 ml.                                             ______________________________________                                    

Directions: Dissolve the 5'-O-palmityl ara-cytidine hydrochloride,sodium citrate and benzyl alcohol in 2,000 ml. water. Add the sodiumbisulfite and adjust the pH 7.0 with the alkali.

EXAMPLE 39

Following the procedure of the preceding Examples 33, 35, and 36,compositions are prepared substituting equivalent amounts of thepharmaceutically acceptable acid addition salts of 5'-O-palmitylara-cytidine for the free base of the examples.

EXAMPLE 40

Following the procedure of the preceding Examples 34, 37 and 38,compositions are prepared substituting equivalent amounts of the freebase of 5'-O-palmityl ara-cytidine hydrochloride for thepharmaceutically acceptable acid addition salt of the examples.

EXAMPLE 41

Following the procedure of the preceding Examples 33, 35, and 36,compositions are prepared substituting equivalent amounts of the otherester compounds of the subject invention or the pharmaceuticallyacceptable acid addition salts of each for 5'-O-palmityl ara-cytidine toprovide similar therapeutic properties.

EXAMPLE 42

Following the procedure of the preceding Examples 34, 37, and 38,compositions are prepared substituting equivalent amounts of the freebase of the other ester compounds of the subject invention or thepharmaceutically acceptable acid addition salts of each for5'-O-palmityl ara-cytidine hydrochloride to provide similar therapeuticproperties.

EXAMPLE 43 Preparation of 5'-O-(p-anisoyl) ara-cytidine hydrochloride

Following the procedure of Example 7, 5'-O-(p-anisoyl) ara-cytidinehydrochloride is prepared by substituting 5'-O-(p-anisoyl) ara-cytidinefor 5'-palmityl cytosine arabinoside.

We claim:
 1. A compound having the following structural formula:##STR125## in which A and B are the same or different radicals selectedfrom the group consisting of H, aliphatic of from 1 to 10 carbon atoms,monocyclic aliphatic of from 4 to 10 carbon atoms, and aromatic of from6 to 10 carbon atoms, and further in which A and B together can make upan aliphatic chain of from 3 to 6 carbon atoms, or the pharmaceuticallyacceptable acid addition salts thereof.
 2. A compound having thefollowing structural formula: ##STR126## in which M is a radicalselected from the group consisting of aliphatic of from 1 to 10 carbonatoms, monocyclic aliphatic of from 4 to 10 carbon atoms, aromatic offrom 6 to 10 carbon atoms, and aralkyl of from 7 to 12 carbon atoms, orthe pharmaceutically acceptable acid addition salts thereof.
 3. Acompound having the following structural formula: ##STR127## wherein M₁is a radical selected from the group consisting of aliphatic of from 1to 10 carbon atoms, aromatic of from 6 to 10 carbon atoms, andaraliphatic of from 7 to 12 carbon atoms, or the pharmaceuticallyacceptable acid addition salts thereof.
 4. A compound having thefollowing structural formula: ##STR128## wherein A₁ and B₁ are the sameor different radicals selected from the group consisting of H, alkyl offrom 1 to 7 carbon atoms, and aromatic of from 6 to 10 carbon atoms, orthe pharmaceutically acceptable acid addition salts thereof.
 5. Acompound of the following structural formula: ##STR129## wherein R₆ is aradical selected from the group consisting of aliphatic of from 1 to 20carbon atoms, aromatic of from 6 to 10 carbon atoms, and araliphatic offrom 7 to 12 carbon atoms, or the pharmaceutically acceptable acidaddition salts thereof.